THE 

GEOLOGICAL"  STORY 


JAA\ES  D.  DANA 


or 


•^   oo 


THE 


GEOLOGICAL  STOKY 


BRIEFLY    TOLD 


BY 

JAMES  i>.  DANA 

"F   (,KiPI.(MiV,         "TEXT-BOOK   OF   G 
CORAL    ISLANDS,"    WORKS   OS    MINERALOGY,    ETC. 


AUTHOR   OF        A    M  A  M   A  I.   OF   (iEol.oiir,         "  TF.XT-BOOK   OF   GEOLOGY,        "CORALS 


XE W   YORK  •:•  CINCINNATI  •:•  CHICAGO 

AMERICAN    BOOK    COMPANY 


Coi-YFK.in.     1  •>!»?>,     KV 

AMERICAN    BOOK   COMPANY. 
GEOL.    STOUY. 


PREFATORY  SUGGESTIONS. 


EOLOGY  is  eminently  an  out-door  science;  for  strata,  rivers, 
^~"^  oceans,  mountains,  valleys,  volcanoes,  cannot  be  taken  into  a 
recitation  room.  Sketches  and  sections  serve  a  good  purpose  in  illus- 
trating the  objects  of  which  the  science  treats,  but  they  do  not  set 
aside  the  necessity  of  seeing  the  objects  themselves.  The  reader  who 
has  any  interest  in  the  subject  should  therefore  go  for  aid  in  his 
study  to  the  quarries,  bluffs,  or  ledges  of  rocks  in  his  vicinity,  and  all 
places  that  illustrate  geological  operations.  At  each  locality  accessi- 
ble to  him  he  should  observe  the  kinds  of  rocks  that  there  occur ; 
whether  they  consist  of  layers  or  not ;  and  their  positions,  whether  the 
layers  are  horizontal, —  the  position  they  had  when  made ;  or  whether 
inclined,  —  a  slope  in  the  beds  being  evidence  of  a  subterranean 
movement  like  that  which  takes  place  in  mountain-making. 

Geology  teaches  that  much  the  larger  part  of  the  rocks  that  con- 
sist of  layers  were  made  through  the  action  of  water ;  and  if  such 
rocks  are  accessible,  it  is  well,  after  learning  the  lessons  of  the  book, 
to  look  among  them  for  evidence  of  this  mode  of  origin,  either  in 
the  structure  of  the  layers,  in  the  nature  of  the  material,  in  markings 
within  the  beds,  or  in  the  presence  of  relics  of  aquatic  life,  such  as 
shells,  bones,  etc.  If  some  of  the  layers  in  a  bluff  consist  of  sand- 
stone, others  are  pebbly,  others  clayey,  and  one  or  more  are  of 


4  PREFATORY    SUGGESTIONS. 

limestone,  the  kinds  of  changes  in  the  waters  that  took  place  to 
produce  such  varied  results  should  be  made  a  point  for  investigation. 

If  an  excavation  for  a  cellar  is  opened  near  an  accustomed 
walk,  it  is  best  to  look  at  the  sections  of  the  earth  or  sands  thus 
made  ;  for  these  sands  are  very  often  in  layers,  and,  in  that  case,  they 
bear  evidence  that  even  there  the  loose  material  of  the  surface  had 
been  arranged  by  water,  either  that  of  the  ocean  or  that  of  a  river 
or  lake. 

When  the  layers  contain  fossils,  a  collection  should  be  made  for 
study ;  for  they  show  what  living  species  populated  the  waters  or 
land  when  the  rocks  were  forming;  and  in  the  height  of  a  single 
bluff  there  may  be  records  thus  made  of  several  successive  popula- 
tions different  from  one  another. 

If  a  beach  or  a  cliff  along  the  ocean  is  accessible,  the  action  of 
the  waves  in  their  successive  plunges  may  be  watched  to  great  ad- 
vantage ;  for  they  are  thus  grinding  up  the  stones  and  sands  of  the 
beuch  and  eroding  and  undermining  the  cliff.  While  viewing  such 
work  on  a  seashore,  it  will  be  a  good  time  to  consider  that  this  but- 
tering goes  on  almost  incessantly  through  the  year,  and  year  after 
year,  and  has  so  gone  on  along  coasts  and  about  reefs  for  indefinite 
ages.  The  cliff  and  the  rocky  ledges  in  the  surf  at  its  base  should  be 
closely  examined,  that  the  amount  and  kind  of  wear  may  lie  appre- 
ciated ;  and  the  action  of  the  water  over  the  beach  should  be  studied 
in'  order  to  understand  why,  after  so  much  grinding,  coarse  sands 
and  often  pebbles  are  still  left. 

If  there  are  sand-flats  exposed  off  the  shores  at  low  tide,  there 
is  a  chance  to  discover  by  what  currents  or  movements  of  the  water 
they  were  formed,  and  whence  came  the  sands  thai  compose  them, 
which  should  be  taken  advantage  of ;  for  these  modern  sand-flats  are 


PKEFATOKV    SUGGESTIONS.  5 

identical  in  kind  and  mode  of  origin,  although  not  in  extent,  with 
the  sand-flats  of  ancient  time  out  of  which  sandstones  have  been 
made ;  the  only  possible  difference  being  that  in  the  earlier  ages  the 
waters  were  everywhere  salt,  and  rivers  gave  little  aid.  And  if  the 
sandy  surface  is  left  rippled  as  the  tide  goes  out,  note  this,  for  ancient 
sandstones  often  contain  such  ripple-marks  over  their  layers  ;  or  if 
the  muddy  portions  are  marked  with  the  tracks  of  Mollusks,  note  this 
also,  for  in  many  rocks  just  such  tracks  occur. 

If  coral  reefs  or  shell  rocks  are  forming  along  the  shores,  as  in 
the  West  Indies,  these  formations  should  receive  .special  study; 
for  many  of  the  old  limestones  of  the  world  were  made  in  the  same 
way. 

If  a  heavy  rain  has  gullied  a  side-hill  or  proved  disastrous  to 
roads,  nere  is  a  fruitful  field  for  study  ;  for  the  gullies  are  minia- 
ture valleys,  and  they  illustrate  how  most  great  valleys  were  ex- 
cavated.—  the  latter  being  as  truly  the  work  of  running  water  as 
the  former.  The  same  gullied  slope  may  exemplify  also  the  for- 
mation of  precipices  and  waterfalls,  of  crested  ridges,  table-topped 
summits,  and  groups  or  ranges  of  mountain  peaks. 

These  are  some  of  the  points  of  easy  observation.  Many  others 
will  occur  to  the  reader  after  a  perusal  of  the  following  pages. 

A  few  labeled  specimens  of  minerals  and  rocks  are  absolutely 
indispensable  for  even  a  partial  understanding  of  the  subject,  and 
the  student  should  buy  or  beg  them,  if  not  able  to  do  the  better 
thing  —  to  collect  them  himself. 

Of  MINERALS:  1,  crystallized  quartz;  2,  two  or  three  quart 7.  pebbles  of 
different  colors ;  l>,  the  variety  of  quartz  called  hornstone  or  m'nt ;  4,  com- 
mon feldspar ;  o,  mica ;  (i,  black  hornblende ;  7,  a  black  or  greenish-black 
crystal  of  augite,  and  better  if  in  a  volcanic  rock ;  8,  garnet ;  9,  tourma- 
line; 10,  ealcite  (carbonate  of  lime),  a  cleavable  specimen;  11,  dolomite,  or 


6  PREFATORY    SUGGESTIONS. 

magnesian  carbonate  of  lime;  12.  gypsum,  or  sulphate  of  lime;  !•">,  pyrite 
(sulphide  of  iron)  ;  14,  magnetite,  or  magnetic  iron  ore;  15,  hematite,  or 
specular  iron  ore ;  16,  limonite,  the  common  iron  ore  often  called  "  brown 
hematite";  17,  siderite,  or  spathic  iron  ore;  18,  chalcopyrite,  or  yellow  cop- 
per ore ;  11),  galenite,  or  lead  ore  (sulphide  of  lead) ;  20,  graphite. 

Of  ROCKS  :  1,  2,  3,  common  compact  limestone  of  three  different  colors, 
one,  at  least,  of  these  specimens  with  a  fossil  in  it ;  4,  chalk,  a  variety  of 
compact  limestone;  5,  (5,  white  and  clouded  granular  or  crystalline  lime- 
stone, of  which  the  ordinary  architectural  marble  is  an  example;  7,  8,  red 
and  gray  sandstone;  9,  conglomerate,  called  also  pudding-stone;  10,  shale, 
such  as  the  slaty  rock  of  the  coal-formation,  and  other  shales  of  the  Silu- 
rian and  Devonian;  11,  slate,  or  argillyte,  that  is,  common  roofing-slate,  or 
writing-slate;  12,  13,  coarse  and  fine-grained  grayish  or  reddish  granite  (to 
be  obtained,  like  marbles  and  sandstones,  in  many  stone-yards) ;  14,  red  or 
gray  quartz-syenyte,  of  which  the  Scotch  "granite"  and  Quincy  "granite" 
are  good  examples;  15,  gneiss,  a  piece  that  has  the  mica  distinctly  in  planes, 
and  hence  is  banded  on  a  surface  of  transverse  fracture ;  l(i,  mica  schist ; 
17,  trap,  an  igneous  rock;  18,  trachyte,  an  igneous  rock;  1!),  lava,  a  cel- 
lular volcanic  rock;  20,  a  piece  of  diatomaceous  or  infusorial  earth. 

The  above-mentioned  minerals  should  at  least  be  accessible  to  a 
class,  if  not  in  the  hands  of  each  student ;  and  it  would  be  well  if 
the  collection  were  larger.  Moreover,  the  instructor,  if  not  a  prac- 
tical geologist,  should  have  by  him  the  writer's  Manual  of  Geology, 
or  some  other  large  work  on  the  science,  in  order  to  be  ready  to 
answer  the  questions  of  inquisitive  learners,  and  add  to  the  exam- 
ples and  explanations. 

The  student  should  possess  a  hammer  and  a  chisel.  The  best 
hammer  has  the  face  square,  flat,  sharp-angled,  and  the  opposite 
end  brought  to  an  edge;  this  edge  should  have  the  same  direction 
with  the  handle  (as  in  the  figure),  if  it  is  to  be  used  for  getting 
out  rock-specimens,  but  be  transverse  to  this,  and  thinner,  if  for 
obtaining  fossils.  The  socket  for  the  handle  should  be  large,  in 


PREFATORY   SUGGESTIONS. 


9 


order  that  the  handle  may  stand  hard  work.  The  chisel  should 
be  a  stone-chisel,  six  inches  long.  Rock-specimens  should  be 
uniform  in  size,  with  straight  sides ;  say 
two  inches  by  three,  or  three  inches  by 
four.  Fossils  had  better  be  separated  from 
the  rock  if  it  can  be  done  safely. 

For  measuring  the  dip,  that  is,  the  slope, 
of  layers,  an  instrument  called  a  clinometer 
is  used,  which  can  be  had  of  the  instru- 
ment makers.  It  is  a  compass  having  a 
pendulum  hung  at  the  center,  the  extrem- 
ity of  which  swings  over  a  graduated  arc. 
Tn  the  best  kind  the  compass  is  three 
inches  in  diameter  and  has  a  square  base. 

A  clinometer  apart  from  the  compass  may  be  easily  extemporized 
by  taking  (see  figure)  a  piece  of  board,  al>c<1,  cut  to  an  exact 
square  (three  or  four  inches  each  side),  hanging  a  pendulum  on  a 
pivot  near  one  angle  (n),  describing  on  the  board,  with  one  leg  of 
the  dividers  on  the  pendulum-pivot,  an  are  of  90°  (1>  to  c),  and  then 
dividing  this  arc  into  nine  equal  parts,  each  to  mark  10°,  and  sub- 
dividing these  parts  into  degrees.  Such  a  clinometer,  well-gradu- 
ated, is  sufficiently  accurate  for  good  work. 

Field  work  of  the  kind  above  pointed  out  makes  the  facts  in  the 
science  real.  It  also  teaches  with  emphasis  the  great  lesson  that  ex- 
isting forces  and  operations  are  in  kind  the  same  that  have  formed 
the  rocks,  the  valleys,  and  the  mountains.  It  thus  prepares  the 
mind  to  appreciate  geological  reasoning  and  comprehend  the  inarch 
of  events  in  the  earth's  history. 

FEW  HAVEN,  CONX.,  April  1,  1895. 


CONTENTS. 


PAfiK 
(iEOLOGY  11 


TAUT  I. 

ROCKS   OR    WHAT  THE   EARTH   IS   MADE   OF      ...      13-38 

I.     MINERALS 10 

Consisting  of  Silica 10 

Silicates 19 

Carbonates 23 

Sulphates 25 

Ores 25 

TI.     KINUS  01-  ROCKS 29 

III.     STRICTI-RE  OF  ROCKS 35 

TAUT  II. 

GEOLOGICAL   CAUSES   AND   EFFECTS 39-121 

I.     MAKING  OF  ROCKS 39 

Contributions  of  Plants  and  Animals 43 

Chemical  Work  of  Air  and  Moisture 58 

Work  of  Winds 01 

Work  of  Fresh  Waters 03 

Work  of  the  Ocean 09 

Work  of  Ice 78 

Work  of  Heat 84 

Solidification  and  Metainorphism 92 

Veins  and  Ore  Deposits 90 

9 


10  CONTENTS 

PAGK 

II.     MAKING  OF  YAU.KYS 101 

By  Erosion 101 

By  Upheaval  of  Mountains 104 

By  Fractures  of  the  Earth's  Crust 104 

III.     MAKING  OF  MOUNTAINS  ANI>  ATTENDANT  EFFECTS     .     .     .  105 

By  Igneous  Ejections 105 

By  Erosion  of  Elevated  Lands 100 

By  Upturnings,  Flexures,  etc 108 

PART   III. 

HISTORICAL  GEOLOGY 122-292 

SUBJECTS  AND  SUBDIVISION* 122 

Classification  of  the  Animal  Kingdom 125 

I.     ARCILKAN  TIME 1:17 

II.     PALEOZOIC  TIME 144 

Cambrian  Era    • 145 

Lower  Silurian  Era 15:5 

Upper  Silurian  Era U>4 

Devonian  Era 170 

Carbonic  Era 184 

Post-Paleozoic  devolution 202 

III.  MESOZOIC  TIME 209 

Triassic  and  Jurassic  Periods 209 

Cretaceous  Period 226 

Post-Mesozoic  Revolution 285 

IV.  CENOZOIC  TIME 2:57 

Tertiary  Era 287 

Quaternary  Era 249 

V.     OBSERVATIONS  ON  GEOLOGICAL  HISTORY 280 

Length  of  Geological  Time 280 

Progress  in  Development  of  the  Earth's  Features    .     .     .  282 

Beginning  and  End  of  the  Earth 288 

Progress  in  Life 284 


GEOLOGY. 


E  word  Geoloiju  is  from  two  Greek  words  signifying 
flu>  start/  of  the  earth.  As  used  in  science  it  means  an 
account  of  tlie  rocks  which  lie  beneath  the  surface  and 
stand  out  in  its  ledges  and  mountains,  and  of  the  loose 
sands  and  soil  which  cover  them ;  and  also  an  account  of 
what  the  rocks  are  able  to  tell  about  the  world's  early 
history.  By  a  careful  study  of  the  nature  and  positions  of 
rocks,  and  the  markings  or  relics  they  contain,  it  has  been 
discovered  how  the  rocks  themselves  were  made;  and  also 
how  the  mountains  and  the  continents,  with  all  their 
variety  of  surface,  were  gradually  formed.  And,  further,  it 
has  been  ascertained  not  only  that  the  earth  had  plants 
and  animals  long  before  Man  appeared,  but  what  were  the 
kinds  that  existed  in  succession  through  the  long  ages. 
The  subjects,  therefore,  of  which  geology  treats  are:  — 

I.  The  KIXDS  OF  ROCKS. 

II.  The  ways  in  which  the  rocks,  valleys,  mountains,  and 
continents  were  made,  —  or  GEOLOGICAL  CAUSES,  AND  THEIR 
EFFECTS. 

11 


12 

III.  The  events  during  the  successive  periods  in  thp 
earth's  history;  that  is,  what  making  of  rocks  Avas  going 
on  in  each  period,  what  making  of  mountains  and  valleys, 
and  what  species  were  living  in  the  waters  and  over  the 
land  in  each,  and  how  the  world  of  the  past  differs  from 
the  world  as  it  now  is,  —  all  of  which  subjects,  and  others 
related,  are  treated  under  the  general  head  of  HISTOIUCAL 
GEOLOGY. 


PART  T. 


ROCKS,  OR  WHAT  THE  EARTH  IS  MADE  OF. 

ROCKS  consist  of  minerals ;  the  ores  and  gems  they  contain 
are  some  of  the  minerals;  and  throughout  the  earth,  to  its 
center,  the  solid  rocks  have  a  crystalline  structure. 

The  most  abundant  element  in  minerals  and  in  the  earth's 
constitution  is  Osi/ycii.  It  makes  part  of  the  atmosphere, 
is  one  of  the  two  constituents  of  water,  and  is  an  essential 
part  of  all  rock-making  minerals.  Owing  to  its  strong 
attractions  for  other  elements,  iron  rusts,  —  that  is,  becomes 
oxidized ;  and  most  iron-bearing  minerals  in  the  rocks  oxi- 
dize, wherever  exposed  to  air  and  moisture.  This  oxida- 
tion produces  the  decay  of  the  rocks,  and  promotes  the 
conversion  of  them  into  gravel,  sand,  and  soil. 

Of  next  importance  in  the  constitution  of  rocks  is  Sili<-<>n 
(named  from  the  Latin  for  Jlitif).  All  the  rocks  excepting 
limestones  contain  silicon  in  combination  with  oxygen,  and 
also  usually  other  elements. 

13 


14  CONSTITUTION    OF    ROCKS. 

Xext  comes  Carbon  (named  from  the  Latin  for  coal).  It 
is  the  chief  ingredient  of  coal  and  one  of  the  constituents 
of  limestone  and  of  mineral  oil  and  gas.  It  is  a  chief 
constituent  also  of  all  animal  and  vegetable  tissues.  In  its 
pure  crystallized  state  it  is  diamond,  the  hardest  of  all 
minerals,  and  also  graphite  or  plmnbafjo  (the  material  of 
lead  pencils),  which  is  among  the  softest  of  minerals. 

Aluminum  (so  named  from  the  Latin  for  clay),  combined 
with  oxygen  and  other  elements,  is  a  chief  constituent  of 
clay,  and  also  of  very  many  of  the  rocks  and  hard  minerals. 

Calcium  (from  the  Latin  for  lime)  is  a  chief  constituent  of 
limestone.  Magnesium,  potassium,  sodium,  are  other  common 
elements  of  rocks. 

Sulphur  occurs  pure  in  nature,  especially  in  volcanic  regions. 
It  is  a  constituent  of  many  ores,  and  also  of  gypsum  among 
rock-making  materials.  Arsenic  is  an  ingredient  of  many 
ores,  but  not  of  any  rock. 

Hydrofjen  (named  from  the  Greek  for  •ir<if<ji--jn'<idnw)  is 
the  element  that  is  combined  with  oxygen  to  form  water. 
It  is  an  essential  constituent  also  of  animal  and  vegetable 
tissues.  It  forms,  with  carbon,  mineral  oil  and  gas. 

The  crystalline  structure  of  the  earth's  minerals  and 
rocks  is  universal.  A  mineral  shows  it  often  in  having 
symmetrically  arranged  facets  over  its  surface,  which  are 
generally  brilliant  in  luster.  Some  of  these  forms  are 
shown  in  the  figure  of  quartz  on  page  17,  of  garnet,  horn- 
blende, and  augite  on  page  22,  and  of  calcite  on  page  L'4. 


ELEMENTS.  It) 

The  crystalline  structure  is  commonly  shown  also  in  the 
presence  of  planes  of  easy  fracture  or  cleavage  in  one  or 
more  directions ;  and  when  in  two  or  three  directions,  in  caus- 
ing many  crystals  to  break  into  fragments  of  symmetrical 
form  when  struck  with  a  hammer.  The  planes  of  fracture 
of  a  broken  bar  of  iron  are  surfaces  of  angular  points  because 
of  this  cleavage,  each  grain  being  an  imperfect  crystal  with 
cleavage  planes ;  and  so  is  the  plane  of  fracture  of  white 
marble,  the  grains  in  the  surface  being  angular  and  lustrous. 
So  it  is  in  granite,  and  through  all  the  earth's  deepest  foun- 
dations wherever  the  rocks  are  not  melted. 

The  crystalline  structure  is  assumed  on  consolidation, 
whether  this  takes  place  from  a  state  of  fusion,  or  of  solu- 
tion, or  of  vapor.  The  vapor  or  moisture  of  the  air  is 
changed  to  crystals  of  water,  or  to  flakes,  which  are  aggre- 
gations of  crystals,  with  every  snowstorm ;  and  the  water 
of  ponds  crystallizes  in  becoming  ice.  Even  the  sand  of 
the  seashore  is  crystalline;  for  every  grain  is  a  fragment 
of  a  crystal. 

If  conditions  are  favorable  for  very  slow,  quiet  consolida- 
tion, single  crystals  of  large  size  may  form;  but  if  too  rapid, 
the  solid  snow  becomes  an  aggregation  of  crystalline  grains. 
This  is  the  condition  of  granite  and  of  all  other  igneous 
rocks  except  the  glassy  ones ;  for  glass,  like  animal  and  vege- 
table tissues,  is  an  exception  to  the  general  rule,  in  being 
non-crystalline.  Even  glass  becomes  crystallized  if  melted 
again  and  sloidtj  cooled;  but  it  is  then  turned  into  stone. 


16  CONSTITUTION    OF    KOCKS. 

It  is  thus  manifest  that  the  principle  \vhich  gives  to  the 
gem  its  beauty  of  form  and  brilliancy  pervades  the  whole 
system  of  material  existence.  The  elements  of  beauty  are 
everywhere. 

I.    MINERALS. 

Minerals  are  distinguished  by  their  chemical  composition. 
Pmt,  in  general,  the  kinds  may  be  determined  by  an  exam- 
ination of  their  color,  hardness,  luster,  specific  gravity, 
and  fusibility. 

When  distinctly  crystallized,  minerals  may  be  distinguished 
also  by  their  crystalline  characters;  for  besides  symmetry 
in  the  general  arrangement  of  the  faces,  there  is,  in  the  same 
mineral  species,  a  like  angle  between  corresponding  faces, 
and  also  between  like  cleavage  directions. 

1 .    Consisting  of  Silica. 

Quartz. — Quartz  is  the  most  common  of  the  materials  of 
rocks.  It  is  well  fitted  for  this  first  place;  for  (1)  it  is 
one  of  the  hardest  of  minerals,  the  point  of  a  knife-blade 
or  edge  of  a  file  making  no  impression  on  it ;  (2)  it  does 
not  melt  in  the  hottest  fire;  and  (3)  it  is  not  dissolved  by 
water,  or  corroded  by  either  of  the  common  acids.  Its  dura- 
bility is  its  great  quality.  With  a  piece  of  quartz  it  is 
easy  to  write  one's  name  on  glass.  Another  quality  of  it, 
distinguishing  it  from  many  minerals  it  resembles,  is  that 
it  breaks  as  easily  in  one  direction  as  another;  that  is.  its 
crystals  have  no  cleavage. 


QUARTZ.  17 

It  is  of  various  colors  and  kinds.  Flint  and  hornstone  are 
dark-colored,  massive  quartz.  The  smooth-surfaced  stones  of 
a  pebble  bank,  whether  white,  brown,  yellow,  or  black,  if 
uniform  (not  speckled)  in  color,  are  almost  all  quartz.  Moun- 
tains thousands  of  feet  high  are  sometimes  made  of  quartz 
rocks.  The  sands  of  a  seashore  are  mostly  quartz,  because 
the  grinding  of  particle  against  particle  which  goes  on  under 
the  heavy  dash  or  swift  flow  of  the  waters  wears  out  all  other 
materials,  and  leaves  only  the  hard  quartz  particles  behind. 

Quartz  is  often  found  in  crystals.  The  figure  annexed 
show's  the  form  of  one  of  them.  It  is  a  regular  six-sided 
prism  (Hi),  with  a  six-sided  pyramid  at  each 
end;  and  it  is  often  as  transparent  as  glass.  Fre- 
quently the  crystals  are  attached  by  one  end  in 
great  numbers  to  a  surface  of  rock,  so  that  this 
surface  is  brilliant  with  little  pyramids  of  quartz  Quartz. 
set  crowdedly  over  it,  or  with  pyramids  raised  on  prisms. 
The  inclination  of  the  face  of  the  prism  to  the  adjoining 
face  of  the  pyramid  is  always  the  same  (141°  47'),  wherever 
the  quartz  crystal  may  come  from.  These  glassy  crystals 
are  wholly  natural  productions,  having  their  forms  perfect 
and  luster  brilliant  when  first  taken  from  the  rocks. 

"While  some  quartz  crystals  are  clear  and  colorless,  others 
have  a  purple  color,  and  these  are  the  amethyst  of  jewelry. 
Others  have  a  light-yellow  color,  looking  like  topaz,  and  are 
called  false  topaz;  and  others  a  clear  smoky-brown  color, 
and  these  are  the  cairngorm  stone  of  Scotland. 
DANA'S  GKOL.  STOKY — 2 


18  CONSTITUTION    OF    ROCKS. 

Agate  is  quartz  in  which  the  color  is  arranged  in  thin 
bands  or  layers  of  different  shades  of  color,  as  white, 
smoky-brown,  red,  etc. 

Quartz,  called  in  chemistry  silica,  is  a  compound  of  silicon 
and  oxygen,  in  the  ratio  of  1  atom  of  the  former  to  2  of 
the  latter,  and  the  chemical  formula  is  therefore  Si02. 

Quartz,  while  so  enduring,  if  pulverized  and  heated,  after 
mixing  it  with  soda,  potash,  lime,  magnesia,  or  oxide  of  iron, 
fuses  easily  and  forms  glass.  Ordinary  glass  is  made  by 
melting  together  quartz  sand  and  soda.  Again,  hot  waters 
containing  soda  or  potash  in  solution  will  dissolve  out  the 
silica  of  silica-bearing  minerals,  and  on  cooling  will  deposit 
it  again.  The  waters  of  hot  springs  often  contain  silica, 
which  they  have  taken,  along  with  soda  or  potash,  from 
some  rock  with  which  they  have  been  in  contact.  Through 
deposits  from  such  solutions  (1)  agates  have  been  made; 
(2)  fissures  in  rocks  have  been  filled  with  quartz,  and  the 
fractures  thus  mended;  and  (3)  the  sands  of  sand  beds  and 
gravel  of  gravel  beds  have  often  been  cemented  into  the 
hardest  of  rocks. 

Opal  is  also  silica,  but  it  differs  from  quartz  in  being 
softer,  of  less  specific  gravity,  and  never  crystallized,  and 
it  is  dissolved  much  more  readily  by  hot  alkaline  waters; 
the  precious  opal  has  a  beautiful  play  of  colors  arising 
from  internal  reflections.  The  silica  of  Diatoms  and  of  the 
deposit  made  by  geysers  (called  geyserite)  is  in  the  state 
of  opal. 


SILICATES.  19 

2.    Silicates. 

Silica,  while  existing  in  rocks  abundantly  as  quartz,  also 
makes,  on  an  average,  a  third  of  all  their  other  minerals, 
limestones  excepted;  that  is,  it  exists  combined  with  other 
substances,  making  various  common  minerals.  These  min- 
erals containing  silica  are  called  silicates. 

Some  of  the  substances  that  are  combined  with  silica  in 
the  common  silicates  are  the  following: 

1.  Alumina.  —  Consists   of   aluminum   and  oxygen   in  the 
ratio  2  :  3,  and  has  therefore  the  formula  A1203. 

In  the  pure  state  it  constitutes  the  mineral  corundum  (a  blue 
variety  of  which  is  the  blue  gem,  sapphire,  and  a  red  variety, 
the  ruby).  It  is  infusible,  like  quartz,  and  harder  than  all 
other  minerals  excepting  the  diamond.  Because  so  hard,  it 
is  ground  up  to  make  emery,  for  grinding  and  polishing  hard 
stones  and  metals. 

2.  Lime.  —  A  constituent  of  all   limestone,  as  well   as   of 
many  silicates.      Quicklime,  which  is  used  for  making  mor- 
tar, is  more  or  less  pure  lime.     Consists  of  one  atom  of  cal- 
cium and  one  of  oxygen,  and  has  therefore  the  symbol  CaO. 

3.  Magnesia.  —  A    constituent    of    Epsom    salt.      Consists 
of  magnesium  and  oxygen  in  the  proportion  1  :  1,  and  has  the 
symbol  MgO. 

4.  Potash.  —  An  ingredient  of  wood  ashes,  hence  the  name. 
Consists  of  potassium  (or  kali  nut)  and  oxygen,  in  the  propor- 
tion 2:1;  its  symbol  is  K20. 


20  CONSTITUTION    OF    ROCKS. 

5.  Soda.  —  An  ingredient  of  the  ashes  of  seaweeds.     Con- 
sists of  sodium  (or  natrium)   and  oxygen  in  the  proportion 
2:1;  its  symbol  is  Na20.      Sodium  and  chlorine  constitute 
common  salt,  the  symbol  being  NaCl. 

6.  Iron   oxides.  —  Consist   of   iron  (ferrum,  in    Latin)   and 
oxygen;  one  oxide  has  the  symbol  FeO,  and  another  Fe2O3. 

Some  of  the  more  common  silicates  are  the  following: 

1.  Feldspar. — A  feldspar  contains,  besides  silica,  the  ele- 
ments of  alumina,  and  of  potash,  soda,  or  lime.  It  is  fusible, 
and  is  therefore  a  constituent  of  most  volcanic  or  igneous 
rocks. 

Feldspar  has  usually  a  white  or  flesh-red  color,  and  some- 
times might  be  mistaken  for  quartz.  But  (1)  it  is  not  quite 
so  hard  as  quartz,  though  too  hard  to  be  scratched  easily 
with  a  knife ;  and,  besides,  (2)  it  melts  when  highly  heated ; 
(3)  it  cleaves  in  one  direction  with  a  bright,  even  surface, 
brilliant  in  the  sunshine,  and  also  in  another  direction 
but  less  easily,  at  right  angles  or  nearly  so  to  the  former. 
While  quartz  has  no  cleavage,  feldspar  has  cleavage  in  two 
directions  transverse  to  each  other. 

Common  feldspar  (called  orthoclase  in  mineralogy)  is  a 
potash  feldspar,  containing  the  elements  of  potash  along  with 
those  of  alumina  and  silica ;  another  form  is  a  soda  feldspar, 
and  is  called  albite,  from  its  usual  white  color;  others  are 
soda-and-lime  feldspars,  and  one  of  these,  called  labradorite, 
is  a  constituent  of  trap,  basalt,  and  other  igneous  rocks ;  and 
another  is  a  lime  feldspar. 


SILICATES.  21 

2.  Mica. — Mica     (often    wrongly    called    isinglass)    splits 
very   easily    into    leaves,   thinner    than    the    thinnest    paper, 
which    are   tough    and    elastic,    and    frequently   transparent. 
It   does   not  melt  easily,  but  fuses  on  the  thin  edges  with 
high  heat.     It   is   the   transparent   material   commonly  used 
in  the  doors  of  stoves.     Some  mica  is  white,  or  gray ;  it  is 
oftener  brownish,  and  very  frequently  black.     Like  feldspar, 
it  contains  the  elements  of  silica  and  alumina,  with  potash. 
The  common  light-colored  kind  is  free  from   magnesia   and 
is   called    mascovite;   the   black  kind  contains  magnesia  and 
iron  and  is  called  biotite. 

3.  Hornblende.  —  Black     hornblende,    when     occurring     in 
rocks,   often   looks  much  like  mica,  showing  lustrous  cleav- 
age surfaces ;  but  it  is  a  brittle  mineral,  and  hence  cannot, 
like  mica,  be  split  into  thin,  flexible  leaves  or  scales  with 
the  point   of   a   knife.      It   makes    very   tough   rocks,    hence 
the  first  part  of  the  name,  horn;  the  rocks  are  heavy  and 
sometimes  look  like  an  ore  of   iron,  hence  the  second  part, 
blende,   a   German  word   meaning   blind  or  deceitful.       It  is 
a  silicate,  that  is,  it  contains  silica,  but  with  it  there  are  iron 
oxide,  magnesia,  and  lime  without  potash.     Hornblende  also 
occurs  of  green,  brown,  and  white  colors.     A  green  radiated 
kind  is   called   actinolite;   a   white   kind,   tremolite ;   a  finely 
fibrous  kind  having  the  fiber  flexible,  asbestus. 

4.  Augite    or    Pyroxene.  —  Augite    is    black    or   dark-green 
pyroxene,    having   the  same   composition   as   hornblende,  and 
differing   only    in   the   shape   of   its   crystals.      It   is   named 


22 


CONSTITUTION    OP   ROCKS. 


from  a  Greek  word  signifying  luster,  because  its  crystals  are 
often  bright,  though  not  more  so  than  those  of  hornblende. 
Two  of  the  crystals  of  hornblende  are  represented  in  Figs. 
2,  3,  and  one  of  those  of  augite  in  Fig.  4.  The  angle  of 
the  prism  of  augite  (or  that  between  /  and  /  in  Fig.  4) 
is  about  87°;  while  the  angle  of  the  prism  of  hornblende 
(between  /  and  /  in  Fig.  2)  is  124^-°;  it  is  mainly  owing 
to  this  difference  that  hornblende  and  augite  have  distinct 
names. 

FIGS.  2-5. 


Minerals . 
Figs.  2,  3,  Hornblende  ;  4,  Augite ;  5,  Garnet  in  inica  schist. 

5.  Garnet.  —  Usually   in  dark-red   crystals,  but   often   also 
black,  and  occurring  imbedded  in  mica  schist  and  other  rocks, 
as   represented   in  Fig.   5.      The   crystals,   here   represented, 
have    12    rhombic    faces,    or    are    dodecahedrons.      Another 
common  form  has  24  faces,   and   is  called  a  trapezohedron. 
The  most  common  varieties  of  garnet  contain  silica,  alumina, 
iron  oxide,  and  lime.     When  transparent  it  is  used  as  a  gem. 

6.  Talc.  —  A    very   soft    mineral,    feeling    greasy    in    the 
fingers,  consisting   of   silica,  magnesia,  and  water.     A   gran- 
xilar  kind  is  soapstone. 


CARBONATES.  23 

7.  Serpentine.  —  A  soft   mineral  or  rock,  usually  greenish, 
of  the  same  constituents  as  talc,  but  in  different  proportions. 

8.  Chlorite.  —  A   soft   dark-green   mineral,  having   the  ele- 
ments  of   talc,  along   with    alumina,    and   often    some    iron 
oxide.     It  is  sometimes  mica-like  in  structure. 

Other  common  silicates  are  staurolite,  whose  crystals  are 
often  crosses;  cyanite,  usually  in  bluish  bladed  forms;  epi- 
dote.  commonly  of  a  yellowish-green  color;  tourmaline,  often 
in  3-  to  9-sided  prisms  of  a  black  color,  the  luster  pitch-like 
on  a  surface  of  fracture;  chrysolite  or  olivine,  a  greenish 
glass-like  silicate  of  magnesia  and  iron,  common  in  some 
igneous  rocks,  especially  basalt. 

3.    Carbonates. 

Carbon  has  been  described  as  one  of  the  constituents  of 
limestone,  mineral  coal,  charcoal,  mineral  gas,  and  mineral  oil. 
One  atom  of  carbon  combined  with  2  of  oxygen  forms  carbon  di- 
oxide, often  called  carbonic  acid;  its  symbol  is  C02.  Carbonic 
acid  is  the  gas  that  escapes  from  ordinary  effervescent 
waters,  such  as  soda  water.  It  is  present  in  the  atmos- 
phere, constituting  3  volumes  in  every  10,000.  Compounds 
of  carbonic  acid  are  called  carbonates. 

1.  Calcite. — Calcite  is  carbonate  of  lime,  also  called  calcium 
carbonate;  its  formula  is  CO2  +  CaO  (or  CaC03).  It  occurs  in 
crystals  that  break  easily  in  three  directions,  affording  forms 
with  rhombic  faces,  like  Fig.  6 ;  the  angles  between  the  faces 
are  105°  5'  and  74°  55'.  A  very  common  form  is  called  dog-tooth 


24  CONSTITUTION    OF   ROCKS. 

spar;  the  shape  is  shown  in  Fig.  7.  Another  kind  is  a 
6-sided  prism  with  a  low  pyramid  at  either  end  (Fig.  8). 
Calcite  is  easily  scratched  with  the  point 
of  a  knife.  Most  limestone  is  more  or  less 
pure  calcite.  When  calcite  or  limestone 
is  burnt,  carbonic  acid  escapes  as  a  gas, 
and  the  lime  is  left.  This  lime  is  the 

so-called    quicklime,    for    making    mortar. 
Calcite. 

AVhen  a  grain  of  calcite  is  put  into  dilute 

hydrochloric  acid,  carbonic  acid  gas  is  given  off  freely, 
producing  a  brisk  effervescence,  and  the  calcite,  if  it  is  pure, 
becomes  wholly  dissolved.  By  means  of  (1)  its  efferves- 
cence with  acid,  (2)  its  low  degree  of  hardness,  (3)  its 
infusibility  in  the  hottest  fire  and  its  burning  to  quicklime 
instead  of  fusing,  calcite  or  limestone  is  easily  distinguished 
from  feldspar  and  other  minerals.  The  cleavages  in  crystals 
of  calcite  also  separate  it  from  feldspar;  for  the  number  of 
directions  is  three,  and  the  angle  between  them  is  about  105° 
instead  of  about  90°.  Limestone  is  mostly  massive  calcite, 
more  or  less  impure,  but  partly  dolomite. 

2.  Magnesian  Limestone,  or  Dolomite.  —  Limestone  sometimes 
contains  magnesia  in  place  of  half  of  the  lime,  and  it  is  then 
called  in  mineralogy,  dolomite,  after  Dolomieu,  a  French 
geologist  of  the  last  century.  Dolomite,  or  magnesian  lime- 
stone, does  not  effervesce  freely  unless  the  acid  is  heated,  and 
in  this  respect  it  differs  from  calcite.  In  aspect,  calcite  and 
dolomite  are  closely  alike. 


SULPHATES   AND    ORES.  25 

4.    Sulphates. 

Sulphur,  when  combined  with  oxygen  in  the  proportion 
1  :  3,  forms,  along  with  water,  the  strong  acid,  sulphuric  acid, 
called  often  oil  of  vitriol. 

Gypsum.  —  Gypsum  is  a  sulphate  of  lime  (or  calcium  sul- 
phate) containing  water.  It  is  one  of  the  ingredients 
deposited  by  sea  water  on  evaporation.  Occasionally  it 
forms  large  rock  masses.  The  mineral  crystallizes  in  rhom- 
bic and  arrow-head  forms,  and  has  an  easy  cleavage  in  one 
direction.  It  is  soft,  pearly  in  luster,  and  white  to  gray 
and  black  in  color.  When  fine  granular,  and  fitted  for 
making  vases  or  for  other  ornamental  use,  it  is  called 
<il<ibaster. 

No  other  sulphate  occurs  in  rock  masses.  Barite,  or  barium 
sulphate,  also  called  heavy  spar,  is  a  frequent  associate  of 
ores  in  veins.  Copperas,  or  green  vitriol,  is  an  iron  sulphate, 
—  a  common  result  of  the  decomposition  of  iron  ores  contain- 
ing sulphur. 

5.    Ores. 

Ores  include  those  metal-bearing  minerals  that  are  of  eco- 
nomical value.  The  metal  in  many  ores  is  in  combination 
with  sulphur  or  oxygen,  but  in  some  with  arsenic,  antimony, 
and  other  elements,  or  with  carbonic  acid,  sulphuric  acid, 
phosphoric  acid,  and  other  acids. 

The  following  are  a  few  of  the  common  ores:  — 

1.    Pyrite.  —  Pyrite    has    nearly   the    color    and    luster   of 


26  CONSTITUTION   OF    ROCKS. 

brass.      It   is    so    hard    that    it   will    strike   fire    with    steel 
(whence  its  name,  from  the  Greek  for  fire),  and  in  this  it 
differs   from   a  yellow   ore   of  copper,  called   chalcopyrite  or 
copper  pyrites,  which  it   much   resembles.      It 
is  very  often  in  cubes,  like  Fig.  9.     It  consists 
of  sulphur  and  iron,  nearly  48  parts  by  weight 
in  100  being  iron;  the  chemical  symbol  is  FeS2. 
pyrite.  Both  of  the  constituents  have  a  strong  affinity 

for  oxygen;  and  consequently  pyrite  often  changes  to  vitriol 
or  an  iron  sulphate,  or  to  the  oxide  of  iron  called  limonite. 
It  is  of  no  use  as  an  ore  of  iron,  because  of  the  difficulty 
of  separating  the  sulphur;  but  it  is  often  employed  for  the 
making  of  vitriol.  It  is  the  most  generally  distributed  of  all 
metallic  minerals,  occurring  in  particles  through  most  rocks, 
crystalline  as  well  as  uncrystalline.  Owing  to  the  tendency 
to  alteration  just  mentioned,  it  has  caused  the  destruction  or 
disintegration  of  rocks  over  the  earth's  surface  to  a  greater 
extent  than  any  other  agency. 

2.  Magnetite,  or  Magnetic  Iron  Ore.  —  An  iron-black  oxide 
of  iron,  having  a  black  powder.  It  is  attractable  by  the 
magnet.  It  often  occurs  in  black  octahedrons.  It  is  com- 
mon in  northern  New  York,  in  Orange  County,  New  York, 
in  Sussex  County,  New  Jersey,  and  in  many  other  regions, 
where  it  constitutes  beds  of  great  thickness,  and  is  worked 
for  making  iron.  It  consists  of  oxygen  and  iron  in  the  pro- 
portion of  4  atoms  of  the  former  to  3  of  the  latter  (Fe304), 
and  contains  72  parts  of  iron  in  100, 


ORES.  27 

3.  Hematite,  or  Specular  Iron  Ore.  —  An  oxide   of   iron,   of 
iron-black  color  when  in  crystals,  but  often  bright  red  when 
massive,  the  powder  being  red.     Red  ocher  is  earthy  hema- 
tite.    It  is  not  strongly  attracted  by  a  magnet.     Like  magnet- 
ite, it  occurs  in  great  beds  in  northern  New  York,  in  the  Mar- 
quette  region,  near  Lake  Superior,  in  Michigan,  and  in  many 
other  places.     It  consists  of  oxygen  and  iron  in  the  propor- 
tion of  3   atoms  of  the   former  to   2   of  the  latter  (Fe203,) 
and  contains,  when  pure,  70  parts  by  weight  of  iron  in  100. 

Nearly  all  rocks  of  a  reddish  or  red  color  owe  their  color 
to  this  oxide  of  iron. 

Hematite  and  magnetite  occur,  with  small  exceptions,  in 
beds  instead  of  veins.  When  the  beds  are  vertical  or  nearly 
so,  they  look  like  veins. 

4.  Limonite.  —  A  brown,  brownish-yellow,  or  black  ore  of 
iron,   affording    a   brownish-yellow   powder;    it    is    sometimes 
called   brown   hematite.      Yellow   ocher    is    impure    or    earthy 
limonite.     It   differs   in   composition  from   hematite   only  in 
containing  water.     When  heated,  the  water  is  driven  off,  and 
it  becomes   red,   and   is   then   hematite   in   composition.      It 
contains,   when  pure,   about   60   per   cent   of    iron.     It   is   a 
result  of  the  decomposition   of   other  iron   ores,   and   forms 
great  beds  in  some  regions,  as  near  Salisbury  in  Connecticut, 
and  in  Richmond,  Massachusetts.     It  is  often  found  in  bogs, 
and  is  then  called  bog  iron  ore.     Limonite  is  often  dissemi- 
nated  through  clays,  giving   them  a  yellowish   or   brownish 
color ;   and  such  clays  turn   red   when  heated,  because   they 


28  CONSTITUTION    OF    ROCKS. 

lose  the  water  which  makes  limonite  differ  from  hematite. 
For  this  reason,  bricks  are  usually  red.  Clay  for  making 
white  pottery  must  contain  no  iron. 

5.  Siderite,  or  Spathic  Iron  Ore.  —  A   gray  to   brown   iron 
carbonate,  without  metallic  luster,  consisting  of  oxide  of  iron 
and   carbonic   acid.     When  pure,  about  48  parts  in  100  are 
iron.      It   occiirs    crystallized,   and    also   in    impure   massive 
nodular  forms.     The   iron   ore  of   many  coal  regions  is  this 
massive  nodular  variety.     It  is  a  heavy  mineral  (the  specific 
gravity  3.5   or   above),  and   by  this   quality  it   may  be   dis- 
tinguished from  other  grayish  or  brownish  stones.     In  heated 
hydrochloric  acid  it  effervesces,  owing  to  the  escape  of  car- 
bonic  acid.     This   ore,    like   limonite,    is   sometimes   present 
sparingly  in  clays. 

6.  Chalcopyrite,    or   Yellow    Copper    Ore.  —  A    brass-colored 
mineral    consisting    of    sulphur,    iron,   and    copper,   about    a 
third   of    which   is   copper.     It    is    scratched    easily   with   a 
knife,    and    affords    a     dark-green    powder,     differing     thus 
from   pyrite,   the   mineral   it   most    resembles.      It   is   some- 
times mistaken  for  gold;   but,  unlike  gold,  it  is  brittle.     It 
occurs  for  the  most  part  in  veins  with  other  ores. 

7.  Galenite,    or   Lead    Ore.  —  A   lead-gray   ore,   brittle    and 
easily  pulverized,  and   affording  a  lead-gray  powder,  consist- 
ing of   sulphur   and   lead,   the   lead   making  over   eighty-six 
per  cent.     It  often  cleaves  into  cubic  or  rectangular  forms. 
It   is  the   common   kind   of    lead   ore.     It   often   contains   a 
little  silver,  and  then  is  worked   as  a  silver  ore.     It  occurs 


LIMESTONE    AND    SANDSTONE.  29 

iii  cavities  in  limestones,  in  northern  Illinois,  Wisconsin, 
and  Missouri,  in  Leadville,  Colorado,  and  in  Derbyshire, 
England.  It  is  often  found  also  in  veins.  At  Leadville, 
and  at  other  places  in  the  Rocky  Mountains,  the  deposits  in 
limestone  are  directly  connected  with  veins,  and  are  part 
of  the  results  of  vein-making. 

8.  Malachite.  —  Green  copper  carbonate,  often  accompany- 
ing other  copper  ores.  Azurite  is  a  blue  copper  carbonate, 
much  less  common. 

II.    KINDS   OF   ROCKS. 

The  following  are  the  characters  of  some  of  the  common 
kinds  of  rocks  :  — 

1.  Limestone ;     Magnesian    Limestone.  —  These    rocks    are 
partly   described   on   pages   23    and    24.      They   are   of  dull 
shades  of   color,  from  white  through   gray,  yellow,  red,  and 
brown   to   black,   and  of    all   degrees   of    texture,   from   the 
compactness  of  flint  to  a  coarse  granular   texture.     The  test 
by  acids,  by  heat,  and  by   use   of  the  point   of   a  knife   in 
trial  of  the  hardness,  are  the  means  of  distinguishing  lime- 
stones   from    other    rocks.      Chalk    is    limestone.      Ordinary 
marble  is  limestone,  and   sometimes   the   magnesian   kind. 

The  different  kinds  of  limestone  are  called  calcareous 
rocks,  from  the  Latin  calx,  meaning  lime. 

2.  Sandstone.  —  Sandstone  is  a  rock   made  of   sand.     The 
sand  may  be  quartz,  like  the  sand  of  most  seashores ;  or  it 


30  KINDS    OF   ROCKS. 

may  be  powdered  granite,  or  other  powdered  rock.  Sand, 
when  gathered  into  beds  and  consolidated,  makes  sandstone. 
Sandstones  are  the  most  common  of  rocks.  They  have  vari- 
ous dull  colors,  from  white  through  gray,  yellow,  and  brown 
to  brownish-red  and  red. 

3.  Conglomerate.  —  A   conglomerate  or  pudding  stone  is  a 
consolidated  gravel  bed,  —  gravel  being  sand  mixed  with  peb- 
bles or  small  stones.     The  stones  are  sometimes  large,  even 
a  foot  in  diameter.     They  are  often  of  quartz,  sometimes  of 
other  hard  rocks,  and  occasionally  of  limestone. 

4.  Shale.  —  Shale  is  a  fine  mud  or  clay  consolidated  into 
a  rock   having   a   slaty   fracture,  but  less   evenly  slaty  and 
less  firm  than  true  slate.     The  colors  vary,  like  the  colors 
of  mud  or  clay,  from  gray  and  yellowish  shades  through  red 
and  brown  to  black.     Black  is  a  common  color,  because  the 
plants  and  animals  that  live  and  die  in  the  mud  or  over  it 
contain  carbon,  the  chief  element  of   coal,   and    contribute 
portions  of  carbonaceous  substances  to  the  mud.     Such  black 
shales,  when  burnt,  usually  become  white  or  nearly  so,  because 
the  vegetable  or  animal  material  is  then  burnt  out.     For  the 
same  reason  black  limestones  afford  white  quicklime. 

The  loose  earthy  material  of  the  world,  in  and  out  of  the 
water,  is  mostly  either  sand,  gravel,  mud,  or  clay ;  and  tlms 
it  has  been  through  all  ages.  Sand  is  finely  pulverized  rock. 
Mud  is  the  same,  for  the  most  part,  but  finer ;  and  it  may  con- 
tain rock  that  is  decomposed  as  Avell  as  pulverized.  Clay  is  a 
fine  kind  of  mud;  it  is  mainly  either  pulverized  feldspar 


CRYSTALLINE   ROCKS.  31 

along  with  quartz  in  fine  grains,  or  else  decomposed  feldspar 
with  more  or  less  quartz.  It  comes  from  the  pulverizing  of 
granite,  gneiss,  and  other  rocks  containing  feldspar,  or  from 
their  decomposition.  Clay  often  contains  iron;  and  when 
burnt  to  make  brick  it  becomes  red.  Gravel  is  mixed  sand 
and  pebbles. 

The  consolidation  of    sand  makes   sandstones;   of    pebble 
beds,  conglomerates;  of  fine  mud  or  clay,  shale. 

5.  Argillaceous   Sandstone.  —  When   sands   are   clayey,   the 
beds  make,  when  consolidated,  a  clayey,  that  is,  argillaceous, 
sandstone  (argilla,  in  Latin,  meaning  clay).     Such  sandstones 
usually  break  into  thin  slabs,  in  which  case  they  are  said 
to  be  laminated   sandstones ;    and,  if   of   sufficient  hardness, 
they  make  good  flagging  stones  for  sidewalks.     The  common 
flagging  stone  used  in  New  York  and  adjoining  states  is  an. 
argillaceous  sandstone. 

6.  Slate.  —  Slate,  or  argillyte,  differs  from  shale  in  break- 
ing much  more  evenly,  and  being  much  firmer.     The  slates 
used  for  roofing  are  examples. 

7.  Granite.  —  Granite   is   one  of  the   crystalline   rocks,  its 
ingredients  being,  not  worn  grains  like  those  of  a  sandstone 
or  conglomerate,  but  crystalline   grains,  all  having  been  ren- 
dered  crystalline   together  by  a  process   in  which   heat  was 
concerned  (pp.  39,  42).     It  consists  of  grains  of  three  miner- 
als,   quartz,   feldspar,    mica,    mixed    promiscuously    together. 
The  quartz  grains  are  usually  grayish  or  smoky  in  color  (com- 
monly of  a  darker  tint  than  the  feldspar),  and  have  no  cleav- 


32  KINDS    OF    ROCKS. 

age.  The  grains  of  feldspar  have  cleavage,  and  therefore 
show  smooth,  sparkling  surfaces  when  a  fragment  of  granite 
is  exposed  to  the  sun,  and  their  color  is  usually  white  or 
flesh-red.  The  mica  is  much  softer  than  the  feldspar,  and 
with  a  point  of  a  knife  blade  its  grains  may  be  divided  into 
thin,  flexible  scales ;  its  colors  are  white,  brownish,  or  black. 

8.  Gneiss.  —  Gneiss   has  the  same  constituents  as  granite; 
but  these  constituents  are  arranged  more  or  less  in  planes, 
and,  owing  to   the  mica,  the   rock    splits  into  thick  layers, 
and  on   a  cross    fracture   appears    banded.      On   account   of 
its  splitting  into  layers  gneiss  is  said  to  be  a  schistose  rock 
(this   term   being   derived   from   a   Greek   word. meaning   to 
divide,  and  pronounced  as  if  spelt  shistose).     This  schistose 
structure  is  the  only  one  distinguishing  it  from  granite.     It 
is  somewhat  like  the  laminated  structure. 

9.  Mica   Schist. —Mica    schist    has   the   same   constituents 
as  granite  and  gneiss,  but  the  quartz  and  mica  are  by  far 
the  most  abundant,  especially  the  mica ;    and  on  account  of 
the  large  proportion  of  mica,  mica  schist  divides  into  thin 
layers.     It  glistens  in  the  sunshine,  owing  to  the  scales  of 
mica.     Sometimes   the   scales   of  mica  are  too   small    to   be 
distinct,  and  contain   some  water   in  combination,  and  then 
it  is  called  hydromica  schist. 

The  rocks,  granite  and  gneiss,  and  gneiss  and  mica  schist, 
pass  into  one  another  through  indefinite  shadings.  There 
are  granites  that  are  slightly  gneiss-like,  and  others  of  all 
grades  to  true  gneiss ;  and  there  are  all  grades  from  gneiss 


CRYSTALLINE   ROCKS.  38 

to  mica  schist,  so  that  it  is  sometimes  difficult  to  say 
whether  a  rock  should  be  called  granite  or  gneiss,  and 
whether  another  should  be  called  gneiss  or  mica  schist. 
Again,  mica  schist  shades  off  into  hydromica  schist  and 
into  argillyte,  or  clay  slate,  as  the  crystalline  texture  is  less 
and  less  apparent. 

10.  Syenyte.  —  Some   granite-like  rocks  contain  hornblende 
in  place  of  the  mica,  with  little  or  no  quartz,  and  such  kinds 
are  called  syemjte.     The  hornblende  is  grayish-black,  greenish- 
black,  or  black,  and  differs  from  black  mica  in  being  brittle, 
and  hence  in  not  affording  thin,  flexible  scales.     If  quartz  is 
present  in  abundance,  the  rock  is  called  quartz-syenyte.     The 
so-called  granite  of  the  Quincy  quarries,  near  Boston,  and  the 
red  Scotch  granite  imported  for  monuments,  are  quartz-syenyte. 

11.  Syenyte-Gneiss  ;  Hornblende  Schist.  —  Syenyte-gneiss  dif- 
fers from  ordinary   gneiss  in  containing  hornblende  instead 
of   mica.     Hornblende  schist  is  a  black,  slaty  rock  consisting 
mainly  of  hornblende. 

12.  Trap,    Basalt,    Lavas,    or    Volcanic    Rocks.  —  Trap    and 
basalt   are   igneous   rocks ;    that   is,    they    have   cooled  from 
fusion,    like    the    lavas    of    a    volcano.      Such    rocks    have 
come   to  the   surface  in   a  melted  state,  through  an  opened 
fissure,    from   some   deep-seated    region   of   liquid   rock,    and 
have  sometimes  flowed  from  the  fissure  over  the  adjoining 
country.      The  part  filling  a  fissure  is  called  a  dike.     Trap 
is    a   dark-colored,  heavy    rock,   more   or   less   crystalline   in 
texture.     The  most  common   variety  consists  of  a  lime-and- 

DANA'S  GKOL.  STORY  —  3 


34  KINDS   OF   KOCKS. 

soda  feldspar  (called  labradorite,  from  Labrador,  where  it  was 
first  found)  and  augite,  along  with  grains  of  magnetite.  It  is 
the  rock  of  the  Palisades  along  the  west  side  of  the  Hud- 
son River  above  New  York,  of  Mount  Holyoke  near  North- 
ampton, and  of  various  hills  and  ridges  in  the  Connecticut 
Valley ;  of  many  ridges  in  the  vicinity  of  Lake  Superior, 
and  over  the  western  slope  of  the  Rocky  Mountains;  of  the 
Giant's  Causeway  on  the  north  coast  of  Ireland,  and  Staffa 
on  the  western  coast  of  Scotland ;  and  it  is  common  over  the 
globe.  Basalt  is  a  similar  rock  containing  scattered  grains 
of  chrysolite  or  olivine. 

Some  trap  contains  small  nodules  consisting  of  different 
minerals.  These  nodules  fill  cavities  that  were  made  by 
expanding  vapors  while  the  rock  was  still  melted.  This 
variety  of  trap  is  called  amygdaloid,  because  the  little 
nodules  sometimes  have  the  shape  of  almonds  (amygdalam, 
in  Latin,  meaning  almond.)  Trap  and  basalt  frequently 
occur  in  columnar  forms,  as  at  the  Giant's  Causeway,  many 
places  in  the  Lake  Superior  region,  near  Orange,  New 
Jersey,  and  elsewhere. 

Volcanic  rocks,  called  lavas,  are  those  that  have  been 
ejected  in  a  melted  state  from,  or  about,  an  open  vent  called 
a  crater  (from  the  Latin  for  bowl).  Eruptions  around  the 
crater  make  the  fire  mountain,  or  volcano. 

A  large  part  of  the  common  lavas  are  similar  in  composition 
to  trap  and  basalt,  although  often  they  are  very  cellular 
rocks,  and  sometimes  resemble  much  the  scoria  of  a  furnace. 


STEATIFIED    KOCKS.  35 

Other  volcanic  and  igneous  rocks  are  mainly  feldspar  in 
composition,  and  as  they  therefore  contain  little  or  no  iron, 
they  are  less  heavy  than  trap  or  basalt.  Their  specific 
gravity  is  mostly  2.5  to  2.8,  while  that  of  the  trap  series 
is  2.8  to  3.2.  A  common  kind,  rough  on  a  surface  of 
fracture,  is  called  trachyte;  and  another,  pontaining  isolated 
crystals  of  feldspar,  is  porphyry.  Rocks  made  out  of  vol- 
canic sands  are  called  tufas. 


III.     STRUCTURE    OF   ROCKS. 

1.  Stratified  Rocks.  —  Most  rocks  consist  of  layers  piled 
one  upon  another ;  and  the  series  in  some  regions  is  thousands 
of  feet  in  height.  Figure  10  represents  a  bluff 
on  the  Genesee  River  at  the  falls  near 
Rochester.  In  this  section  Nos.  1 
and  2  are  sandstone;  No.  3, 
green  shale ;  No.  4,  limestone ;  Section  on  Genesee  River. 

No.  5,   shale;    No.  6,  limestone;   No.  7,  shale;  No.  8,  lime- 
stone again. 

Another  example  is  here  presented  (Fig.  11)  from  the 
Colorado  canon.  The  height  of  the  pile  of  layers  in  view 
is  over  3110  feet;  but  the  river  flows  2755  feet  below, 
and  hence  the  whole  height  of  the  wall  is  5865  feet. 
Still  another  example  from  the  Colorado  region  is  given  on 
page  103. 

It  is  to  be  noted  that  (1)  the  layers  were  made  one  after 


36 


STRUCTURE   OF   ROCKS. 

FIG.  11. 


Part  of  the  wall  of  the  Colorado  Canon,  from  a  photograph  by  Powell's 
Expedition. 

another,  beginning  with  the  lowest;  that  (2)  the  successive 
layers  correspond  to  successive  intervals  of  time  in  geologi- 
cal history. 

Rocks  consisting  thus  of  beds  are  called  stratified  rocks, 
from  the  Latin  stratum,  meaning  bed. 

But  layer  and  stratum  in  geology  have  not  the  same  mean- 
ing. In  Fig.  10  the  lower  sandstone  bed,  No.  1,  consists  of 
many  layers;  together  they  make  a  stratum.  No.  3  is  another 


UNSTRATIFIED   ROCKS.  37 

stratum,  —  one  of  shale;  No.  4,  another,  —  one  of  limestone, 
and  also  made  up  of  many  layers ;  and  so  on.  Thus  there 
are  ei<jht  strata  (strata  being  the  plural  of  stratum)  visible 
in  the  bluff;  and  each  consists  of  many  layers.  All  the 
layers  of  one  kind,  lying  together,  make  one  stratum. 

Sandstone,  shale,  conglomerate,  and  limestone  are  the  most 
common  kinds  of  stratified  rocks.  Gneiss  and  mica  schist 
also  are  stratified,  although  crystalline  in  texture. 

2.  Unstratified  Rocks.  —  Unstratitied  rocks  are  not  made 
up  of  layers.  The  granite  about  the  Yosemite,  in  California, 
is  in  lofty  mountains  and  mountain  domes,  showing  no  dis- 
tinct bedding  or  stratification ;  and  the  same  is  the  character 
of  most  granite.  The  trap  rocks  of  the  Palisades,  on  the 
Hudson,  rise  boldly  from  the  water  and  have  no  division 
into  layers;  but,  instead,  a  vertical  division  into  imperfect 
columns,  a  common  feature  of  such  trap  rocks,  illustrated 
on  the  next  page.  It  is  not,  however,  true  that  all  igneous 
rocks  are  ?<?*stratified;  for  where  lavas  have  flowed  out  in 
successive  streams  over  a  region,  those  streams  have  made 
successive  beds,  and  the  rocks  are  truly  stratified.  But  the 
term  stratified  rocks  is  usually  applied  'only  to  the  kinds 
not  of  igneous  origin. 

The  columnar  structure  of  some  trap  rocks  is  well  illus- 
trated in  the  following  view  of  a  scene  on  the  shores  of 
Illawarra  in  New  South  Wales,  Australia.  While  stratifi- 
cation has  come  from  the  successive  formation  of  beds, 
these  columns  are  a  result  of  the  cooling.  Cooling  causes 


38 


STRUCTURE   OF   ROCKS. 


contraction,  and  the  contraction  of  the  solid  rock,  as  cooling 
goes  on,  produces  the  fractures.  These  fractures  are  always 
at  right  angles,  or  nearly  so,  to  the  cooling  surfaces.  Where 


FIG.  12. 


Basaltic  columns,  coast  of  Illawarra,  New  South  Wales. 

the  rock  fills  vertical  fissures,  the  columns  are  horizontal. 
Even  sandstones  have  been  rendered  columnar  where  over- 
laid by  beds  of  trap,  or  when  they  have  been  subjected 
otherwise  to  heat. 


PART    II. 


GEOLOGICAL   CAUSES  AND  EFFECTS. 

UNDER  the  head  of  Causes,  Geology  treats  of  the  ways 
in  which  (1)  rocks,  (2)  valleys,  (3)  mountains  and  continents 
were  made ;  or,  in  general,  the  means  through  which  all 
changes  have  been  brought  about. 

I.   MAKING  OF  ROCKS. 

THE  rocks,  briefly  described  in  the  preceding  pages,  have 
been  made  by  the  following  methods: 

1.  Rocks  formed  from  Fusion. — Igneous  rocks  are  here  in- 
cluded, or  those  that  have  cooled  from  a  melted  state  either 
beneath  the  surface  of  the  earth  or  after  ejection  at  the  sur- 
face. They  are  generally  crystalline,  though  sometimes  glassy, 
in  texture,  each  grain  in  the  former  case  being  a  separate  crys- 
tal; yet  the  small  grains  are  generally  so  crowded  together 
that  they  have  nothing  of  the  external  forms  of  crystals,  and 
very  often  are  too  minute  to  be  easily  distinguished.  Igneous 
rocks  are  of  small  extent  and  importance  over  the  globe  as 
compared  with  those  made  through  the  action  of  water, 

39 


40  MAKING   OF    ROCKS. 

2.  Rocks  made  by  Deposition  from  Waters  holding  the  Mate- 
rial of  them  in  Solution.  —  Waters  containing  lime  often  de- 
posit it,  and  so  make  a  kind  of  limestone.  As  examples : 
waters  percolating  through  the  limestone  roofs  of  caverns, 
as  they  evaporate  on  the  roof,  form  long  pendent  cones  or 
cylinders  of  limestone  called  stalactites  (from  the  Greek  for 
to  distil);  and  the  same  waters,  dropping  to  the  floor  of  the 
cavern,  there  evaporate  and  produce  a  bed  of  limestone  called 
stalagmite. 

There  are  many  springs,  and  some  rivers,  in  the  world, 
whose  waters  are  calcareous.  Such  waters  petrify  the  moss, 
leaves,  and  nuts  of  swamps,  and  sometimes  make  thick  beds 
of  limestone,  which  are  very  porous,  and  irregular  in  thick- 
ness and  texture,  called  calcareous  tufa,  and  also  travertine. 
On  Gardiners  River,  in  the  Yellowstone  Park,  at  the  summit 
of  the  Rocky  Mountains,  such  deposits  are  forming,  and  the 
river  is  thus  made  into  a  series  of  waterfalls.  But  such 
beds  of  limestone  are  of  even  less  extent  and  importance 
than  igneous  rocks.  None  of  the  great  limestones  of  the 
world  were  thus  made. 

Waters  often  hold  traces  of  silica  in  solution,  especially 
if  they  are  hot  and  alkaline,  and  they  deposit  this  silica 
again,  making  siliceous  beds  and  petrifactions.  Some  facts 
on  this  point  are  mentioned  beyond,  among  the  effects  of 
heat  in  rock-making.  Cold  water  seldom  deposits  silica 
unless  where  there  are  the  remains  of  siliceous  infusoria,  as 
mentioned  on  page  54. 


MECHANICAL   AND   ORGANIC    AGENCIES.  41 

3.  Rocks  made  by  the  Mechanical  Agency  of  Waters  and 
Winds,  exclusive  of  Limestones.  — -  Far  the  larger  part  of  rocks 
are  fragmented  rocks;  that  is,  they  are  rocks  made  out  of 
fragments  of  older  rocks.  The  finest  mud  or  clay  consists 
of  fragments  of  rock  material,  and  hence  a  shale  —  a  rock 
made  from  fine  mud  or  clay  —  is  a  f ragmental  rock  as  much 
as  a  sandstone  or  a  conglomerate. 

A  large  part  of  the  fragments,  or  the  sand,  pebbles,  and 
mud,  were  made  by  the  wearing  action  of  moving  waters ;  and 
hence  such  material  is  called  detritus,  from  the  Latin,  mean- 
ing it-orn  oat.  The  agency  of  greatest  effect  and  longest 
action  in  past  time  has  been  the  ocean;  that  of  next  im- 
portance, ricertt;  that  next,  winds.  But,  preparatory  to  these 
agencies,  the  air,  moisture,  and  the  sun's  heat  have  been 
quietly  at  Avork  giving  aid  in  the  reduction  of  rocks  to  frag- 
ments or  grains;  and  thus  the  ocean,  rivers,  and  winds  have 
found  much  loose  material  ready  for  them,  instead  of  being  left 
to  make  all  that  was  required  for  their  work  in  rock-making. 

The  sand,  gravel,  and  mud  or  clay  of  which  rocks  have 
been  made  were  in  general  deposited  as  a  sediment  from  the 
waters  of  the  ocean  or  rivers,  as  will  be  explained  further 
on ;  and  hence  sandstones,  conglomerates,  and  shales  are  called 
alimentary  rocks. 

4.  Rocks  made  mainly  or  wholly  of  Organic  Remains,  that  is, 
of  the  Remains  of  Plants  or  Animals.  —  (1)  The  great  limestones 
of  the  world  are  of  organic  origin;  also  (2)  some  siliceous 
deposits;  and  (3)  the  coal-beds  and  peat-beds  of  the  world. 


42  MAKING   OF   ROCKS. 

Many  sandstones  and  shales  contain  more  or  less  of  such 
remains.  Plants,  shells,  and  other  distinguishable  relics  of 
living  species  found  in  rocks  are  called  fossils,  or  organic 
remains.  They  are  sometimes  called  also  petrifactions,  which 
means  made  into  stone;  but  not  always  rightly  so,  for  many 
fossils  consist  of  essentially  the  same  material  that  com- 
posed the  living  species.  Wood  is  sometimes  changed  to 
stone;  and  this  is  then  a  true  petrifaction. 

5.  Metamorphic  Rocks.  —  Fragmented  rocks,  such  as  sand- 
stones, shales,  and  conglomerates,  and  also  limestones,  have 
sometimes  been  altered  (or  metamorphosed),  over  regions  of 
great  extent,  to  crystalline  rocks,  such  as  gneiss,  mica  schist, 
granular  limestone,  or  architectural  marble;  and  these  crys- 
talline rocks  are  hence  called  metamorphic  rocks,  the  word 
metamorpliic  meaning  altered.  Some  granites  are  metamor- 
phic, while  other  granites  are  igneous  rocks. 

The  following  order  of  description  is  here  adopted :  — 

1.  The  ways  in  which  plants  and  animals  have  contributed 

to  rock-making. 

2.  The  results  from  the  quiet  working  of  air  and  moisture. 

3.  The  work  of  winds. 

4.  The  work  of  rivers. 

5.  The  work  of  the  ocean. 

6.  The  work  done  by  ice. 

7.  The  work  of  heat. 

8.  Solidification  and  metamorphism  of  rocks. 

9.  Veins  and  ore  deposits. 


LIMESTONES.  43 


1.   Ways   in   which   Plants   and   Animals    have    contributed    to 
Rock-making. 

1.  Making  of  Limestones. 

The  animal  relics  that  have  contributed  most  to  lime- 
stones are  shells,  corals,  crinoids,  and  foraminifers.  These 
are  skeletons  of  animals,  that  is,  stony  portions  of  the  body, 
either  made  internally  in  the  same  manner  as  the  bones  of  a 
dog  are  made,  or,  like  a  shell,  made  externally  as  a  covering 
for  the  animal.  When  the  animal  dies,  the  relics  pass  to 
the  mineral  kingdom  and  are  used  in  rock-making;  and,  as 
stated  before,  nearly  all  the  limestones  have  thus  been  made. 

Corals  and  crinoids  are  exclusively  oceanic  species  of  ani- 
mals ;  but,  while  this  is  true  also  of  most  shells  and  fora- 
minifers, there  are  some  kinds  that  flourish  in  fresh  waters, 
and  among  shells  some,  like  the  snail,  live  over  the  land. 

1.  Shells.  —  Shells  are  the  skeletons  of   animals  related  to 
the  oyster,  clam,  snail,  and  cuttle-fish,  —  animals  that  have  a 
soft  fleshy    body,   and  hence   are   called   Mollusks,   from   the 
Latin  mollis,  soft.     The  shells  serve  to  protect  the  soft  body 
and  give  it  rigidity. 

2.  Corals.  —  Coral   is,  for  the   most    part,  the   skeleton   of 
polyps,  the  most  flower-like  of  animals,  and  it  is  an  internal 
skeleton.      One  of  the   branching  corals,  covered  over   (one 
branch   excepted)  with  its  numerous  little   flower-animals,  is 
represented  in  Fig.  13.     Branching  corals  of  this  nature  are 


44 


MAKING    OF    ROCKS. 


common  in  the  tropical  Pacific  and  the  West  Indies,  and  are 
called  Madrepores.  Another  kind,  massive  instead  of  branch- 
ing, is  shown  in  Fig.  14.  The  whole  surface  is  a  surface  of 
flower  animals  or  polyps;  in  reference  to  its  star-like  cells 
this  kind  is  called  an  Astrcea.  The  expanded  animals  (only 

FIG.  13. 


Madrepora  aspera.    D. 


part  of  which  in  the  figure  are  in  this  state)  are  like  flowers 
also  in  their  bright  colors.  The  little  petal-like  arms  (tenta- 
cles), in  Fig.  13,  are  tipped  with  emerald-green,  in  the 
living  state;  some  Astrseas  are  purple  or  crimson,  with  an 


LIMESTONES. 


45 


FIG.  14. 


FIG.  15. 


Astraea  pallida.     D. 

emerald  center,  and  others  have  other  bright  tints.  While  so 
much  like  Mowers  in  appearance,  polyps  are  wholly  animal 
in  nature.  Each  polyp  has  a  month 
at  the  center  above,  as  shown  in 
Fig.  14;  and  it  eats  and  digests  like 
other  animals.  Another  kind  of  coral 
is  represented  in  Fig.  ir>,  without  the 
animal ;  it  shows  the  radiating  plates 
in  the  cup-shaped  cavity  at  the  top. 
Still  another,  somewhat  larger,  ellipti- 
cal in  shape  instead  of  cylindrical, 
and  in  the  living  state,  is  presented 
in  Fig.  16.  The  mouth  is  a  very  long  one,  and  the  arms  or 
tentacles  which  serve  to  push  in  the  prey  it  captures  are 


Thecocyathus  cylindraceus. 


46  MAKING   OF   KOCKS. 

also  long.     It  owes  much  of  its   power  of   capturing   to  the 
stinging  qualities  of  these  tentacles. 

The  arrangement  of  the  tentacles  of  a  polyp  around  a 
center,  and  also  that  of  the  plates  inside  of  the  coral  cup, 
is  radiate;  and  hence  Polyps,  like  some  other  kinds  of  life, 
are  often  called  Radiate,  animals. 

FIG.  16. 


Flabellum  pavoninum. 

3.  Crinoids.  —  Crinoids  also  are  flower-like  animals.  They 
were  once  exceedingly  abundant  in  the  seas  of  the  world, 
but  now  are  rarely  found.  Two  of  the  kinds  are  rep- 
resented in  Figs.  17  and  18,  the  first  an  ancient  species, 
and  the  second  a  modern  one  from  the  seas  of  the  West 
Indies.  The  arms  above  are  arranged  around  a  center 
like  the  petals  of  a  flower,  and,  like  them,  they  may  be 
opened  out  wide  or  closed  up  so  as  to  look  like  a  bud ;  and 
this  opening  or  closing  the  animal  does  at  will.  Below  the 
radiating  part,  or  body,  there  is  a  stem,  sometimes  a  foot 
or  more  long,  which,  if  the  animal  is  alive,  is  planted  below  on 


LIMESTONES. 


the  solid  rock,  or  in  the  mud  of  the  sea-bottom.  Crinoids  differ 
in  many  respects  from  polyps.  One  point  is  this:  the  coral 
which  a  polyp  makes  is  all  one  piece,  whether  massive  or 
branching;  while  the  stony  skeleton  of  the  crinoid  is  in 
multitudes  of  pieces.  The  stem  is  a  pile  of  little  disks 
often  circular  and  looking  like  button  molds,  as  in  Fig.  17; 

FIGS.  17, 18. 


IT 


Crinoids. 

Fig.  17,  Woodocrinus  elegans ;   18,  Pentacrinus  cai>ut-Medusa?,  now  living  in  the  West 
Indies  ;  a-d,  calcareous  disks  or  plates  of  the  stem,  showing  their  5-sided  form. 

but  sometimes  5-sided,  as  in  Figs.  18  a,  b,  c,  d,  showing  some 
of  the  forms.  The  arms  also  are  made  up  of  stony  pieces. 
The  cross  lines  on  the  arms  in  the  above  figures  indicate 
the  number  of  pieces  of  which  each  is  made.  The  pieces 
are  held  together  by  animal  membrane  as  long  as  the 
animal  lives ;  but  when  it  dies,  the  pieces  usually  fall  apart, 
and  are  scattered  by  the  moving  waters. 


48 


MAKING    OF   ROCKS. 


4.  Rhizopod  Shells,  or  Foraminifers.  —  Khixopods  are  among 
the  simplest  of  all  animals;  they  are  very  minute  animals 
that  have  no  organs  of  sense,  and  not  even  a  mouth  to 
eat  with. 

Some  of  the  shells  are  represented  in  Figs.  19  to  32 ;  all  are 
much  enlarged  excepting  those  in  Figs.  31,  32  a,  b.  These 
animals  have  the  faculty  of  extending  out,  at  will,  feelers 


FIGS.  19-32. 

23  /^  24 , 


Shells  of  Rhizopods. 

Fig.  19,  Orbulina  universa;  20,  Globigerina  rubra ;  21,  Textularla  g-lobulosa ;  22,  Rotalia 
globulosa;  22  a,  side  view  of  Rotalia  Boucana ;  23,  Grammostomum  phyllodes  ;  24,  n, 
Frondicularia  annularis  ;  25,  Triloculina  Josophina ;  26,  Nodosaria  vtilgaris  ;  27,  Lituola 
nautiloides  ;  28,  a,  Flabellinarugosa ;  29,  Chrysalidina  gradata ;  30,  a,  Cuneolina  pavonia  ; 
81,  Nunimulites  minimtilaria  ;  32  a,  b,  Fusulina  cylindrica. 


over  the  body  that  are  a  little  root-like,  and  hence  they  are 
called  Rliizopods,  from  the  Greek  for  root-like  feet.  An 
enlarged  view  of  one  of  the  species,  with  the  fiber-like  arms 
extended,  is  shown  in  Fig.  33.  A  particle  of  food  corning  in 
contact  with  this  network  of  root-like  processes  is  enveloped 
and  digested,  the  gelatinous  substance  of  the  body  being 
nearly  homogeneous,  and  all  parts  of  it  possessing  the 


LIMESTONES.  49 

power  of  digestion.  All  of  the  shells  in  Figs.  19-33 
excepting  those  in  Figs.  31,  32  a,  b,  are  no  larger  than  the 
finest  grains  of  sand;  and  yet  they  FIG.  SB. 

contain  a  number  of  cells,  each  of 
which  corresponds  to  a  separate 
one  of  the  Rhizopod  animals. 

Fig.  31  is  a  large  foraminifer 
shaped  like  a  com,  and  the  Latin 
for  coin,  mnnntntf,  suggested  for  it 
the  name  it  bears,  —  a  Nummtdite.  Rotaha  veneta. 

Shells,  corals,  crinoids,  and  foraminifers  consist  almost 
solely  of  carbonate  of  lime,  the  material  of  limestone ;  and 
hence  their  consolidation  makes  limestone.  Shells,  corals, 
and  crinoids  are  usually  more  or  less  ground  up  under  the 
action  of  the  waves  or  currents  of  the  ocean,  and  thus 
reduced  to  fragments  or  sand,  before  they  are  consolidated. 
Much  coral  limestone  of  existing  seas  —  the  rock  of  coral 
reefs  —  shows  no  trace  of  the  corals  of  which  it  wras  made, 
because  all  were  ground  by  the  aid  of  the  waves  and  cur- 
rents to  a  coral  sand  or  coral  mud  before  consolidation. 
But  in  other  cases  the  rock  contains  fragments  of  the 
corals  or  crinoids,  and  sometimes  entire  specimens.  Fig. 
34  shows  the  aspect  of  a  crinoidal  limestone  when  the 
crinoidal  remains  are  not  wholly  ground  up;  the  disks  and 
cylinders  are  portions  of  the  stems  of  the  crinoids.  The 
coral  reefs  of  the  Pacific  are  coral-made  limestones,  and 
some  of  them  are  hundreds  of  square  miles  in  area  and 
DANA'S  GEOL.  STORY — 4 


50 


MAKING    OF   ROCKS. 


many  hundreds  of  feet  in  thickness.  But  besides  corals, 
the  shells  of  the  coral-reef  seas  contribute  largely  to  the 
limestone  material. 

Foraminifers   are   so   minute   that  they  need  no   grinding 
FI«.  34.  in  order  to  make  a  fine- 

grained rock.  They  live 
principally  near  the  sur- 
face of  the  ocean,  and  their 
remains  are  especially 
abundant  over  the  sea-bot- 
tom down  to  a  depth  of 
twelve  or  fifteen  thousand 
feet,  as  has  been  proved  by 
soundings  in  the  Atlantic 
between  Ireland  and  Newfoundland,  and  elsewhere.  Chalk  is 
made  mainly  of  foraminifers,  at  depths  from  a  few  hundreds 
of  feet  to  thousands ;  and  it  is  now  being  made,  and  has  been 
through  ages  past,  over  the  bottom  of  the  ocean. 

There  are  also  some  plants,  of  the  order  of  Seaweeds, 
that  secrete  lime,  and  which  have  thereby  contributed  to 
rock-making.  Among  these  are  included  (1)  coral-making 
plants,  called  Nullipores,  so  named  from  the  fact  that, 
while  looking  like,  corals,  they  have  no  pores  or  cells; 
(2)  Corallines,  which  are  related  to  Nullipores,  but  have 
delicate  jointed  stems;  (3)  Coccoliths,  microscopic  calcareous 
disks,  which  are  very  abundant  over  some  parts  of  the 
ocean's  bottom  and  occur  also  in  shallower  waters. 


Crinoidal  Limestone. 


SILICEOUS   ROCKS. 


51 


2.   Making  of  Siliceous  Rocks  or  Masses. 

Some  of  the  minutest  and  simplest  of  plants  and  animals 
make  stony  skeletons  of  silica  instead  of  carbonate  of  lime, 
and  hence  form  out  of  their  stony  skeletons  beds  of  silica 
instead  of  beds  of  limestone.  Although  minute,  often  requir- 
ing a  high  microscopic  power  to  make  them  visible,  such 
species  have  thus  been  large  contributors  to  rock-making 
through  all  geological  history.  Many  of  them  are  remark- 
able for  their  beauty  of  form  and  texture. 

The  plants  here  included  are  called  Diatoms.  Nearly  all 
are  too  minute  to  be  distinguished 
without  a  lens.  Some  of  the  forms 
are  shown,  highly  magnified,  in 
the  annexed  figures,  35^40.  They 
are  strange  forms  for  plants,  and 
still  are  known  to  be  of  this  king- 
dom of  life.  They  have  lived  in 

i  ,  n         Diatoms  highly  magnified. 

such  numbers  over  the  bottoms  of 

Fig.  35,   Pinniilaria  peregrina,   Rich- 

shallow    ponds,    marshes,    and    Seas,         mond,  Va. ;   86,   Pleurosigma  an- 

gulatum,  ibid. ;  37,  Actinoptychus 

that  the   infinitesimal  shells   have 


.  35-40. 


senarius,  ibid.;  38,  Melosira  suleata, 
ibid.  ;  a,  transverse  section  of  the 
same  ;  39,  Grammatophora  marina, 
from  the  salt  water  at  Stoningtou, 
Conn. ;  40,  Bacillaria  paradoxa, 
West  Point. 


sometimes    made    beds    scores    of 

yards  in  thickness.     The   material 

of  such  beds  looks  like  the  finest 

of  chalk.     Owing   to   the  hardness   and  extreme  fineness  of 

the   grains,  it  was  used  as  a  polishing  powder   long  before 

it  was  discovered  that   each  particle  was  the  skeleton  of  a 


52 


MAKING   OF   ROCKS. 


microscopic  water  plant.  It  is  obtained  from  the  bottoms  of 
many  marshes,  and  is  sold  for  polishing;  the  packages  in 
the  shops  from  beds  making  the  bottom  of  shallow  ponds 


Richmond  Infusorial  Earth. 

a,  Pinnularia  peregrina;  b,  o,  Odontidium  pinmilatum ;  <7,  Grammatophora  marina; 
e,  Spongiolithis  appemliculata ;  /,  Meloslra  sulcata ;  g,  transverse  view,  Id.;  h,  Actino- 
cyclus  Ehrenbergii ;  i,  Coscinodiscus  apiculatus  ;  j,  Triceratiuin  obtusuin  ;  k,  Actinop- 
tychus  undulatus;  I,  Dictyocha  crux;  m,  Dictyocha;  >i,  fragment  of  a  segment  of 
Actinoptychus  senarius  ;  o,  Navicula ;  p,  fragment  of  Coscinodiscus  gigas. 

or  marshes   are   sometimes  labeled  Silex.      A  bed  of   great 
extent  in  Virginia,  near  Richmond,  is  in  some  places  thirty 


SILICEOUS   ROCKS. 


53 


feet  thick;  and  a  little  of  the  dust,  under  the  miscroscope 
of  Ehrenberg  of  Berlin — who  first  made  known  the  nature 
of  these  polishing  powders  —  presented  the  appearance 
shown  in  Fig.  41.  All  these  forms  were  in  the  field  of  his 
microscope  at  one  time.  Nearly  every  particle  is  a  Diatom 
or  a  fragment  of  one.  Some  Diatom  beds  near  Monterey, 
in  California,  have  a  thickness  exceeding  fifty  feet. 

Among  animals  making  siliceous  skeletons,  the  following  are 
examples.  (1)  A  kind  illustrated  in  Figs.  42-44,  related 
to  the  Bhizopods,  but  dif- 
fering in  the  forms  of 
the  shells,  and  in  their 
consisting  of  silica. 

(2)  Most  Sponges,  for 
sponges  are  animal  in  na- 
ture. Ordinary  sponges 
are  made  of  horn-like 

fibers ;  but  in  the  living  state  these  fibers  are  covered  thinly 
with  a  gelatinous  coating  which  is  in  reality  a  layer  of 
animal  cells  but  little  higher  in  grade  than  Rhizopods. 
In  many  of  them  these  horny  fibers  are  bristled  with 
minute  spicules  of  silica  of  various  forms.  A  few  of  these 
forms  are  shown  in  Figs.  45-59.  Some  of  the  oblong  pieces  or 
fragments  in  Fig.  41,  page  52,  are  spicules  of  ancient  sponges. 

Other  sponges  consist  wholly  of  fibers  of  transparent  silica, 
excepting  a  thin  coating  of  animal  material.  One  of  these 
siliceous  sponges  from  the  bottom  of  the  East  India  seas 


COOC} 

coco 
Ooorc 
PCCOC 
ooocc 

oooco 

COO 


Radiolarians. 


54 


MAKING   OF   ROCKS. 


is  shown  in  Fig.  60,  half  the  natural  size.  The  delicacy  of  the 
structure  might  hardly  be  inferred  from  the  figure;  for  the 
sponge  looks  as  if  made  of  spun  glass,  and  as  if  too  fragile  to 
be  handled.  Such  siliceous  sponges  are  common  over  the 
bottom  of  the  ocean,  and  at  various  depths  below  the  reach 
of  the  waves,  whose  violence  they  could  not  withstand. 

The  flint  of  the  world,  or  liornstone  as  the  most  of  it  is 
called  (page  17),  is  nearly  pure  silica  (or  quartz),  and,  like 
quartz,  it  scratches  glass  easily.  It  is  found  imbedded  in 
limestones  and  other  rocks.  It  has  been  made  mostly  out  of 


FKJS.  45-59. 


Siliceous  Spicules  of  Sponges. 

spicules  of  Sponges,  Diatoms,  and  Radiolarians,  without  any 
unusual  degree  of  heat.  This  shows  that  such  deposits, 
when  under  water,  may  be  partly  dissolved  by  the  cold  waters, 
and  then  consolidated  without  any  external  aid  beyond  that 
afforded  by  the  saline  ingredients  of  the  waters.  By  the 
same  means  shells  and  other  fossils  have  often  been  changed 
to  quartz,  or  have  undergone  a  true  petrification. 

The  harder  parts  of  Worms,  Insects,  Spiders,  Centipedes, 
and  Crustaceans  have  contributed  to  the  material  of  rocks, 
or  occur  imbedded  in  them ;  so  also  do  the  bones  and  scales 


FIG.  60.    Euplectella  speciosa,  or  Glass  Sponge, 


56  MAKING    OF    ROCKS, 

of  Fishes  and  Reptiles ;  the  bones  and  occasionally  the 
feathers  of  Birds  ;  the  bones  and  teeth  of  Quadrupeds  of  vari- 
ous kinds ;  and  remains  of  various  other  forms  of  life.  Besides, 
the  tracks  of  animals  are  occasionally  met  with  on  the  sur- 
faces of  layers,  from  those  of  Worms  and  Insects  to  those 
of  Quadrupeds  and  Man. 

The  living  species  of  the  globe  that  have  contributed  most 
to  rocks  are  those  of  the  waters,  because  rocks  are  mainly 
of  aqueous  origin ;  and  chiefly  marine  species,  because  the 
greater  part  of  rock-making  has  l>een  the  work  of  the  ocean. 

Oceanic  life  is  in  greatest  profusion  along  the  shallow 
waters  off  shore,  down  to  a  depth  of  one  hundred  and  fifty 
feet ;  the  corals  which  make  coral  reefs  in  our  present  seas  do 
not  live  much  below  this.  But  there  is  abundant  life  at 
greater  depths,  and  life  is  not  wanting  even  at  a  depth  of 
15,000  feet  or  more.  Crabs  with  good  eyes  have  been  obtained 
from  the  sea-bottom  at  a  depth  of  5000  feet;  lobsters  without 
eyes  at  a  depth  of  5000  to  12,000  feet ;  and  a  few  living 
Mollusks  from  a  depth  exceeding  12,000  feet.  Besides  these 
species,  there  are  through  all  these  depths  living  Corals, 
Crinoids,  and  delicate  siliceous  Sponges  related  to  that  figured 
on  page  55.  But  Rhizopods  are  the  most  abundant  species 
(page  48),  and  with  these,  there  are  Radiolarians  and  the 
minutest  and  simplest  of  plants,  Diatoms  and  Coccoliths. 
The  Diatoms  live  in  the  ocean  near  the  surface,  but  sink  to 
the  bottom  as  they  die.  The  same  is  true  of  a  large  part 
of  the  Rhizopods. 


PEAT-BEDS.  57 

3.    Making  of  Peat-beds. 

Deposits  of  leaves,  stems,  and  other  remains  of  plants  are 
always  found  in  the  water  in  marshy  areas,  where  spongy 
mosses  of  the  genus  Sphagnum  are  growing  luxuriantly, 
besides  other  water-loving  plants  small  and  large,  with  some 
kinds  that  can  stand  the  water,  but  would  thrive  better  were 
it  drier.  The  moss,  which  is  the  chief  plant  in  the  increasing 
deposit,  has  the  faculty  of  dying  below  while  growing  above; 
and  thus  its  dead  stems  may  be  many  yards  long,  while  the 
living  part  at  top  is  only  about  six  inches  long.  The  small 
plants  and  shrubs,  and  the  trees,  if  such  there  be,  shed  their 
leaves  and  fruit  annually,  and  these  fall  into  the  water. 
Annual  plants  die  each  year,  and  their  stems  are  buried 
with  the  leaves.  All  the  plants,  the  mosses  excepted,  sooner 
or  later  die,  and  thus  branches  and  trunks  are  added  at 
times  to  the  accumulation  in  progress.  Moreover,  the  bones 
of  Birds  and  Quadrupeds  and  remains  of  Insects  and  other 
inferior  kinds  of  life  become  buried  in  the  deposit. 

The  materials  of  plants  buried  under  water  undergo  a 
kind  of  smothered  combustion.  They  become  black,  then  are 
reduced,  below,  to  a  pulpy  state,  or  rarely  to  an  imperfect 
coal ;  and  the  mass  thus  altered  constitutes  what  is  called 
peat. 

Dry  woody  material  consists  one  half  of  carbon,  the 
main  constituent  of  charcoal,  along  with  two  gases,  oxygen 
and  hydrogen ;  and  in  the  change  the  proportion  of  the  gases 


58  MAKING   OF   ROCKS. 

to  the  carbon  is  diminished  about  one  fifth.  The  black  color, 
one  result  of  the  change,  is  due  to  the  carbon,  as  in  the  case 
of  the  black  color  of  soils,  many  muds,  and  black  clayey  and 
calcareous  rocks. 

The  bed  of  peat  sometimes  increases  until  it  is  scores  of 
yards  in  depth.  Peat  swamps  are  common  over  all  conti- 
nents out  of  the  tropics.  Even  the  smaller  swamps  have 
usually  a  peaty  bottom.  The  areas  become  superficial  when 
the  marshes  dry  up. 

The  Dismal  Swamp  in  Virginia  and  North  Carolina  is  a 
peat  swamp  from  one  end  to  the  other ;  and  no  one  has  yet 
ascertained  the  depth  of  the  peat.  Ireland  is  noted  for  its 
peat  swamps ;  the  "  mosses,"  as  they  are  called,  of  the  Shan- 
non, are  fifty  miles  long  and  two  to  three  miles  broad. 

The  world  has  had  its  peat  swamps  in  all  ages  since  the 
first  existence  of  abundant  terrestrial  vegetation;  and  these 
are  the  sources  of  all  its  coal-beds,  each  coal-bed  having  been 
at  first  a  peat-bed.  But  the  kinds  of  plants  concerned  in 
the  making  of  the  peat  swamps  have  varied  with  the 
successive  ages. 

2.   Quiet  Chemical  Work  of  Air  and  Moisture. 

When  rocks  are  wholly  under  water,  whether  it  be  salt  or 
fresh  water,  they  are  generally  protected  from  decay.  But 
if  above  the  water,  so  that  air  as  well  as  moisture  has  free 
access,  nearly  all  become  altered,  and  many  crumble  to  sand 
or  change  to  clayey  earth. 


WORK   OF  AIR    AND   MOISTURE.  59 

Blocks  of  some  kinds  of  sandstone  that  would  answer 
well  for  underwater  structures,  when  left  exposed  to  the 
air  for  a  few  years  fall  to  pieces,  or  peel  off  in  great 
concentric  layers.  Crystalline  limestone  (white  and  clouded 
marble)  in  many  regions  covers  the  surface  with  marble 
dust  from  its  decay.  Gneiss  and  mica  schist  are  among 
the  durable  rocks ;  and  yet  much  of  the  gneiss  and  mica 
schist  of  the  world  undergoes  slow  alteration,  so  that  in 
some  regions  these  rocks  are  rotted  down  or  have  become 
soft  earth  or  a  gravel  to  a  depth  of  fifty  or  a  hundred 
feet,  and  even  two  or  three  hundred  feet  in  tropical  countries. 
This  is  the  amount  of  decomposition  produced  in  those  places 
through  a  very  long  period  of  time,  perhaps  the  whole  time 
from  the  epoch  of  their  elevation  above  the  ocean.  But  it 
is  no  measure  of  the  amount  that  would  have  taken  place 
if  the  decayed  portion  had  been  removed  as  it  was  formed, 
as  has  often  happened;  for,  in  that  case,  alteration  would 
have  proceeded  with  much  greater  rapidity  because  of  the 
freer  access  of  air  and  moisture. 

The  granite  hills  are  often  thought  of  as  an  example  of 
the  everlasting,  as  far  as  anything  is  so  on  the  earth.  But, 
while  there  is  granite  that  is  an  enduring  building  stone,  a 
large  part  of  the  granite  of  the  world  becomes  so  changed 
on  long  exposure  that  the  plains  and  slopes  around  are 
thence  deeply  covered  with  the  crumbled  rock,  and  great 
masses  may  be  shivered  to  fragments  by  a  stroke  of  a  sledge. 
Many  granitic  elevations  over  the  earth's  surface  have  dis- 


60  MAKING   OJT    ROCKS. 

appeared  beneath  their  own  debris.  Much  trap-rock  is  as 
firm  as  the  best  granite.  But  other  kinds  are  rotted  down 
to  a  depth  of  many  feet  or  yards,  and  sometimes  only  here 
and  there  a  ledge  shows  itself  above  the  ground  as  the 
remains  of  ranges  of  hills. 

Even  the  most  solid  trap,  where  exposed  to  the  elements, 
has  a  decomposed  outer  layer,  or  is  weathered,  as  the  change 
is  called.  This  crust  is  often  but  a  line  or  two  deep  and 
has  everywhere  the  same  depth  over  blocks  of  like  kind. 
But  the  uniformity  in  depth  is  owing  to  the  fact  that,  as  the 
elements  eat  inward,  there  is  as  gradual  a  loss  of  the  altered 
grains  over  the  outer  surface. 

Thus  invisible  agencies  are  producing  the  slow  destruction 
of  the  exposed  parts  of  nearly  all  the  rocks  of  the  globe, 
even  to  the  tops  of  the  lofty  mountains.  The  firmer  kinds 
of  slates  (argillyte),  some  hard  conglomerates  and  gneisses, 
and  the  compact  limestones  are  among  the  rocks  that  defy 
the  elements  most  successfully. 

In  this  way  rocks  have  been  prepared  for  the  rougher 
geological  work  carried  on  by  moving  water  and  ice  ;  and 
through  the  same  means  the  earth  or  soil  of  the  world  has 
to  a  large  extent  been  made. 

This  quiet  work  of  air  and  moisture  is  chemical  work ; 
and  it  is  mostly  performed  through,  the  chemical  action 
of  two  ingredients  present  in  them,  —  carbonic  acid  and 
oxygen.  Other  agencies  aid  in  this  slow  destruction,  as 
explained  on  pages  beyond. 


WORK   OF   WINDS.  61 

3.   The  Work  of  Winds. 

The  wind,  or  moving  air,  works  geologically  by  trans- 
portation, by  the  deposition  of  the  material  it  transports, 
and  by  abrading  and  rending  the  rocks  and  other  objects 
in  its  way. 

1.  Transportation  and  Deposition.  —  The  winds  carry  sands 
from  one  place  to  another;  and  wherever  the  earth's  surface 
is  one  of  dry  sand,  and  the  winds  blow  strongest  and  longest 
in  one  direction,  great  accumulations  of  sand  are  made. 
Even  when  the  windows  of  a  house  in  a  city  are  ordinarily 
kept  closed,  the  dust  will  get  in. 

Seashores  are  often  regions  of  sand,  owing  to  the  work 
of  the  waves.  The  heavy  winds  take  up  the  loose,  dry 
sands  and  carry  them  beyond  the  beach,  to  make  ranges 
of  sand  hills,  often  20  to  30  feet  or  more  high.  Thence 
the  hills  frequently  travel  inland,  through  the  same  means, 
sometimes  burying  forests,  as  on  the  west  coast  of  Michi- 
gan, sometimes  overwhelming  villages,  as  in  England  and 
France,  leaving  at  times  only  the  top  of  a  church  spire  to 
mark  the  site.  The  west  winds  have  driven  the  sands  of 
the  Desert  of  Sahara  over  parts  of  Egypt,  and  ancient  cities 
have  thus  been  buried. 

The  stratification  of  a  hill  of  drifted  sands  is  so  peculiar 
that  it  is  easy  to  tell  when  sand  rocks  have  been  formed 
through  the  agency  of  the  winds.  Fig.  61  represents  a  part 
of  a  section  observed  in  the  Pictured  Rocks  on  the  south 


62 


MAKING  OF   KOCKS. 


FIG.  61. 


Part  of  a  Section  of  a  Drift  Sand 
Hill,  showing  the  Stratification. 


shores  of  Lake  Superior.  The  layers  dip  in  many  direc- 
tions. Such  a  structure  is  owing  to  the  accidents  to  which 

the  sand  hills  are  exposed.  A 
heavy  storm  —  perhaps  aided 
by  heavy  waves  at  high  tide  — 
often  carries  away  part  of  a 
hill.  Then  the  winds  build  it 
up  anew,  putting  the  successive 

drifts  —  which  make  the  successive  layers  —  over  the  new 
surface,  differing  much  from  the  first  in  its  slopes.  The 
hill  suffers  from  another  storm,  and  is  again  built  up  during 
the  period  of  quieter  weather  that  follows.  This  may  take 
place  many  times.  The  result  is  the  kind  of  irregularity 
of  stratification  illustrated  in  Fig.  61. 

2.    Abrasion.  —  Sands   carried    by   winds   over   rocks   often 
wear  the  surfaces  deeply,  as  well  exemplified  in  the  semi-desert 

Via.  62. 


Wind-worn  Rocks  of  the  Egyptian  Desert. 

regions  of  southern  California,  Nevada,  and  other  dry  parts 
of  the  west,  in  the  Grand  Traverse  region  near  Lake  Michi- 
gan, and  elsewhere.  This  agency  in  dry  countries  has  scoured 


WORK   OF   FRESH   WATERS.  63 

out  gorges,  shaped  and  undermined  bluffs,  and  thus  given 
to  the  landscape  its  prominent  features.  Fig.  62  illustrates 
the  work  of  the  winds  in  the  Egyptian  desert ;  the  upturned 
ledges  have  had  their  softer  layers  worn  away,  leaving  a 
compact  limestone  layer  as  the  summit  of  each.  Even  the 
harder  rock  yields;  for  the  markings  over  the  surface  indi- 
cate the  positions  of  fossils  that  are  left  projecting  because 
siliceous. 

The  abrading  work,  it  is  to  be  noted,  is  performed  for 
the  most  part  by  the  sand  and  gravel  which  the  air  trans- 
ports. Man  has  taken  the  hint,  and  now  uses  sand  driven 
by  steam  to  etch  on  glass  and  to  carve  granite  and  other 
rocks. 

3.  Rending.  —  The  rending  power  of  moving  air  is  shown 
at  times  in  the  tearing  of  houses  to  pieces  or  taking  off  of 
their  roofs,  in  the  overthrowing  of  walls  and  uprooting  of 
trees.  These  effects  depend,  not  on  any  transported  sand 
in  the  air,  but  on  the  movement  of  the  air  in  mass  against 
the  obstructing  agent. 

4.   The  Work  of  Fresh  Waters. 

Running  water  is  at  work  universally  over  a  continent 
wherever  the  clouds  yield  rain  and  there  is  a  slope  to  pro- 
duce movement;  and  it  acts  with  greatest  energy  where 
the  slope  is  greatest,  or  about  high  hills  and  mountains. 
It  works  at  abrasion,  transportation,  and  deposition,  and 
with  vastly  greater  efficiency  than  moving  air. 


64  MAKING   OF    EOCKS. 

The  waters  of  the  rains,  mist,  and  dew  about  the  mountain 
tops  descend  in  drops  and  rills,  and  then  gather  into  plunging 
streamlets  and  torrents ;  the  many  torrents  combine  below 
into  larger  streams;  and  these,  from  over  a  wide  region, 
unite  to  make  the  great  rivers.  The  Mississippi  has  its 
arms  reaching  westward  and  northward  to  various  summits 
in  the  Kocky  Mountains,  and  eastward  to  the  Appalachians ; 
and  its  greatness  is  owing  to  the  vast  breadth  of  the  area 
it  drains.  Not  only  mountains,  but  all  the  small  elevations 
over  a  land,  and  even  its  little  slopes,  have,  \\liru  it  rains, 
their  rills  combining  into  torrents,  and  these  into  larger 
streams,  which  flow  off  to  join  some  river. 

The  waters  of  the  clouds  no  sooner  drop  to  the  ground 
than  they  begin  to  tear  off  and  carry  away  grains  of  earth  from 
the  rocks  or  slopes.  The  work  over  the  larger  part  of  a  country 
may  be  almost  wholly  suspended  in  the  dry  season ;  but  when 
the  rains  set  in,  the  surface  is  alive  with  its  workers,  small 
and  great.  Torrents  become  increased  immensely  in  depth 
and  force,  and  earth  and  often  rocks  are  torn  up  and  borne 
along  in  vast  quantities. 

The  little  rills  groove  lightly  the  sand  or  gravel  over 
which  they  flow.  The  streamlets,  made  by  the  uniting  rills, 
cut  deeper  and  wider  channels.  The  torrents  produced  from 
the  combined  streams  and  streamlets  gouge  out  and  wear 
away  even  the  harder  rocks,  and,  as  their  volume  increases, 
make  great  valleys.  The  subject  of  the  making  of  valleys 
is  illustrated  on  page  103. 


•\VOI:K  OF  FIIKSH  WATERS.  65 

Where,  along  a  valley,  harder  and  softer  layers  of  rock 
alternate,  one  lying  above  the  other,  the  harder  rocks  wear 
slowly,  while  the  softer  yield  easily ;  and  so  a  valley  is 
made  to  have  abrupt  descents  along  its  channel,  and  the 
stream  goes  in  leaps  or  >.<•«! crfa/lx,  as  it  flows  on  its  way. 
The  harder  rock  at  Niagara,  making  the  top  at  the  falls, 
is  limestone,  and  the  softer  rock  below  is  shale ;  and  the 
wearing  away  of  the  shale  has  preserved  the  verticality  of 
the  precipice,  as  the  erosion  of  the  gorge  has  proceeded,  and 
the  falls  have  moved  up  stream. 

The  more  rapid  the  flow  of  the  water,  the  coarser  the 
detritus  it  can  transport;  and  as  a  stream  slackens  its  rate 
the  coarser  material  falls  to  tin1  bottom,  leaving  only  the 
liner  to  be  carried  on.  First  the  large  stones,  and  then  the 
smaller,  will  drop  as  the  torrent  becomes  less  and  less 
violent:  but  the  earth  and  gravel  may  be  borne  on  to  the 
rivers;  and  these,  in  their  times  of  flood,  may  carry  a  large 
part  of  the  burden  of  earth  to  the  ocean. 

Under  such  a  rough-and-tumble  movement  stones  are  worn 
to  earth  and  gravel,  ami  in  this  pulverized  state  they  may 
continue  the  journey  seaward.  A  single  heavy  rain  storm 
lias  sometimes  so  filled  the  narrow  gorges  of  a  mountain 
that  vast  deluges  of  water,  rocks,  gravel,  and  trees  have 
swept  down,  carrying  away  houses  and  spreading  desolation 
over  the  plains  below. 

Through  the  wearing  effect,  of  rivers  and  their  tributaries, 
reaching  to  every  part  of  a  continent,  the  mountains,  ever 
DANA'S  GEOL.  STOKY  —  5 


66  MAKING    OF    ROCKS. 

since  their  first  emergence,  have  been  on  the  move  to  the 
ocean,  and  we  cannot  judge  of  their  former  height  from 
what  now  exists. 

The  process  of  erosion  is  often  called*  degradation,  because 
mountains  and  hills  are  made  low  by  it ;  denudation,  because 
it  removes  their  exterior;  erosion,  because  it  excavates  river 
channels  and  valleys. 

The  material  transported  by  rivers  is  called  sediment,  or 
that  which  settles  in  the  water;  and  when  it  is  fine  mud, 
silt.  It  is  also  called  detritus,  from  the  Latin  for  -worn  out, 
because  it  is  worn-out  rock. 

The  average  amount  of  sediment  annually  carried  to  the 
borders  of  the  Gulf  of  Mexico  by  the  Mississippi  Elver  has 
been  stated  to  be  812,500,000,000  pounds,  or  enough  to  make 
a  pyramid  a  square  mile  at  base  over  700  feet  in  height. 
This  material  is  deposited  about  the  mouth  of  the  river,  and 
is  gradually  extending  it  farther  and  farther  into  the  Gulf. 

The  fine  sediment  of  rivers  settles  much  more  rapidly 
in  salt  water  than  in  fresh,  and  this  is  one  reason  why 
this  material  is  prevented  from  being  carried  off  to  the 
deep  ocean. 

The  great  area  about  the  mouth  of  a  large  river  over 
which  these  deposits  are  distributed  is  usually  intersected 
by  channels,  and  constitutes  what  is  called  a  delta,  —  so 
named  from  the  name  of  the  Greek  letter  I),  which  has 
a  triangular  form  (A).  Fig.  63  represents  the  delta  of  the 
Mississippi. 


WORK    OF    FRESH    WATERS. 


67 


The  channel  of  the  river  extends  far  into  the  Gulf  of 
Mexico,  and  terminates  in  several  months.  The  delta 
stretches  northward  nearly  to  the  mouth  of  Red  River. 


Delta  of  the  Mississippi. 

The  waves  and  currents  of  the    gulf  act  with  the  currents 
of  the  river  in  the  deposition  of  the  sediment. 

The  Mississippi  is  an  example  of  what  all  rivers  are 
doing,  each  according  to  its  ability.  Some  carry  their 
detritus  to  lakes  to  extend  their  shores,  and  aid  in  filling 
them.  But  much  of  the  detritus  is  left  on  the  various 
river  Hats,  and  this  part  is  called  tdlurlam.  Again,  a  large 


68  MAKING    OF    ROCKS. 

part  reaches  the  ocean,  and  is  distributed  along  the  borders, 
making  sand-flats,  mud-flats,  and  ultimately  good  dry  land, 
to  widen  the  serviceable  area  of  the  continent. 

The  banks  and  bottom  of  a  river  are  generally  made  of 
coarser  or  finer  material,  according  to  its  rate  of  flow  in  the 
different  parts.  Where  it  is  very  slo\v  the  bottom  and  banks 
are  sure  to  be  of  mud,  for  the  very  slow  movement  of  the 
waters  gives  a  chance  for  the  finest  detritus  to  settle ;  but 
if  rapid  it  will  consist  of  pebbles,  if  the  region  contains 
them.  The  bank  struck  by  the  current  is,  in  general,  more 
pebbly  than  the  opposite. 

Rivers  grow  Old.  • —  A  river,  by  its  work  of  erosion  at 
bottom,  and  the  transportation  down  stream  of  the  sedi- 
ment so  made,  is  ever  lowering  its  bed,  and,  therefore,  grad- 
ually diminishing  its  mean  slope.  \Vherever  this  slope 
becomes  so  slight  that  the  lowering  ceases,  the  river  has 
reached  a  level  of  no  icork,  or  base-level.  It  has  grown  old. 
This  is  the  state  of  many  rivers  especially  in  the  part  toward 
the  sea,  and  the  Mississippi  Biver  is  an  example.  In  this 
feeble  stage  any  erosion  at  bottom  that  takes  place  is  bal- 
anced by  the  deposition  of  fine  sediment,  or  silt.  Sometimes 
this  deposition  exceeds  the  amount  carried  off  in  times  of 
floods;  and  then  the  bed  of  the  river  keeps  rising,  from 
year  to  year,  and  the  overflows,  in  flood  times,  disastrously 
extend  their  limits  unless  prevented  by  embankments. 

Lakes.  —  The  action  of  the  waters  of  large  lakes  in  rock- 
making  is  to  a  great  degree  the  same  as  that  of  the 


WORK    OF   THE   OCEAN.  ()9 


T>.    The  Work  of  the  Ocean. 

The  mechanical  work  of  the  ocean  is  carried  forward  chiefly 
through  (1)  its  tidal  movements ;  (2)  its  waves ;  and  (3)  its 
currents. 

1.  Tides.  —  With  each  incoming  tide  the  waters  flow  up 
the  coast  and  into  all  bays  and  mouths  of  rivers,  rising 
several  feet  and  sometimes  yards  above  low-tide  level ;  and 
then,  with  the  ebb,  the  same  waters  flow  back  and  once 
more  leave  the  mud-flats  and  sand-banks  of  the  bays  and 
coasts  exposed  to  view.  This  retreat  of  the  tide  allows  the 
rivers  to  discharge  freely  and  carry  out  their  detritus  to 
sea ;  but  soon  again  the  inflow  stops  the  outward  movement 
and  reverses  it.  During  the  time  of  slackened  flow  the 
waters  drop  their  detritus,  part  about  the  mouth  of  the 
stream,  part  along  the  adjoining  coast,  and  part  in  the  shallow 
waters  of  the  sea  outside. 

The  incoming  tide  is  feeble  in  movement,  swelling  gently 
over  the  land  and  up  the  bays.  It  becomes  rapid  only  where 
it  passes  through  narrow  channels,  in  which  case  the  large 
body  of  water  is  forced  to  make  up  for  the  small  passage- 
way by  moving  at  greater  speed.  But  the  outflowing  tide 
often  moves  rapidly  over  the  bottom  of  bays,  and  especially 
when  a  river  empties  into  the  bay  and  adds  to  the  amount 
of  water.  Besides,  it  takes  up  additional  detritus  from 
the  bottom,  and  bears  it  out  to  sea.  It  thus  prevents  the 


70  MAKING    OF    ROCKS. 

entrances  to  bays  or  harbors  from  becoming  tilled  up  by 
the  deposits  of  the  iiiwashing  tide. 

2.  Waves.  —  The  sea  in  its  quiet  state  is  rarely  without 
some  swell,  which  causes  at  short  intervals  a  gentle  move- 
ment on  the  beach  and  some  rustling  of  the  waters  along 
rocky  shores.  Generally  there  are  waves  and  breakers ;  and 
when  a  heavy  storm  is  in  progress  the  waves  rise  to  a  great 
height  and  plunge  violently  upon  the  beach  and  against  all 
exposed  rocks,  wave  following  wave  in  quick  succession 
through  days  or  it  may  be  weeks  together.  With  each  storm 
the  waves  renew  their  violent  strokes,  and  in  many  seas 
the  action  is  almost  incessant. 

The  plunge  on  the  beach  grinds  the  stones  against  one 
another,  gradually  rounding  them  and  finally  reducing  them 
to  sand,  and  the  sand  to  finer  and  finer  sand.  The  waters 
after  the  plunge  retreat  down  the  beach  underneath  the  new 
incoming  wave;  and  this  "undertow"  carries  off  the  finer 
sand  made  by  the  grinding,  to  drop  it  in  the  deeper  waters 
off  the  coast,  leaving  .  the  coarser  sand  to  constitute 
the  beach. 

Thus  wave-action  grinds  to  powder  and  removes  the  feld- 
spar and  other  softer  minerals  of  the  sand,  leaving  behind 
the  harder  quartz  grains;  and  consequently,  the  sand  and 
pebbles  of  beaches  consist  mostly  of  quartz.  Moreover, 
where  beaches  of  sand  line  a  coast  there  are  offshore  deposits 
of  mud  made  out  of  the  fine  material  carried  seaward  by  the 
undertow.  In  no  age  of  the  world  have  sand-beds  been 


WORK   OF   THE   OCEAN.  71 

formed  without  the  making  of  mud-beds  in  their  immediate 
vicinity. 

The  cliffs,  or  exposed  ledges  of  rock,  are  worn  away  under 
the  incessant  battering  and  afford  new  stones  and  sand  for 
the  beach  and  the  shallow  waters  adjoining.  Most  rocky 
shores,  especially  those  of  stormy  seas,  show,  by  their  rugged 
cliffs,  needles,  arches,  and  rocky  islets,  the  effects  of  the 
storm-driven  waves. 

It  is  to  be  remembered  that  the  ocean,  as  stated  on  page 
58,  often  finds  the  work  of  destruction  facilitated  by  the 
weakening  or  decomposition  the  rocks  have  undergone  through 
the  quiet  action  of  air  and  moisture.  Another  method  of 
destruction  is  explained  beyond  on  page  84. 

The  waves,  as  they  move  toward  the  shores  over  the  shelv- 
ing bottom,  bear  the  sediment  in  the  waters  shoreward,  and 
throw  more  or  less  of  it  on  the  beach ;  and  thus  the  beach 
grows  in  extent.  The  sediment  is,  in  general,  either  what  it 
gets  from  the  battered  rocks  of  the  coast,  or  what  the  rivers 
pour  into  the  sea.  At  the  present  time  the  Atlantic  receives 
an  immense  amount  of  detritus  through  the  many  large 
streams  of  eastern  North  America;  and,  as  a  consequence, 
the  shores  are  extensive  sand-flats  from  New  York  south- 
ward; there  are  generally  long  beaches,  with  shallow  basins 
or  sounds  inside,  and  wide  low  regions  more  inland. 

This  Atlantic  border  has  been  growing  seaward  for  ages 
through  the  means  mentioned,  with  but  little  aid  from  the 
wear  of  seashore  cliffs.  But  in  the  earlier  geological  ages 


72  MAKING    OF    ROCKS. 

this  was  not  so;  for  the  continent  was  to  a  large  extent 
more  or  less  submerged,  and  the  waves  made  a  free  sweep 
over  its  surface,  battering  the  rocks  wherever  within  their 
reach  over  the  wide  area,  and  thus  making  its  own  sedi- 
ment; for  there  were  only  small  streams  on  the  small  lands 
to  give  any  help, 

3.  Wind-made  Currents.  —  The  winds,  especially  the  prevail- 
ing storm  winds,  are  the  chief  source  of  strong  currents  along 
sea-borders,  as  well  as  of  high  waves  and  careering  breakers. 
They  drive  the  waters  before  them,  moving  them  to  consider- 
able depths ;   and  where  these  currents  sweep  along  a  coast, 
they  gather  detritus  from  the  bottom  and  from  the  beaches, 
and   also    from    the    discharging    rivers,   and    drop    it    again 
where   obstructing   shores  or   capes   are  met.     This   drifting 
action  often  makes  long  sand-spits  and   sand-bars  nearly  all 
the  way  across  the  mouth  of  a  bay.     New  York  Bay  is  thus 
shut  in,  the   entrances   being   narrow   channels   through  the 
sand-bars.     These  channels  are  kept  open  by  the  outflow  of 
the   waters    of    the    Hudson    River   and    some   New    Jersey 
rivers,  together  with  those  of  the  outflowing  tide. 

4.  Contributions  to  Sea-border  Sands  and  Deposits  by  the  Life 
of  the  Waters.  —  In  the  warmer  seas  of  the  world  MoU-uuJcx  are 
very   abundant.      The   heavier   storm-waves   tear   them   from 
the   muddy  bottom   in   or   over  which   they  are   living,  and 
throw  them  on  the  beach.     There   they  are   exposed  to  the 
incessant    grinding  which  stones   and  ordinary   sands   expe- 
rience  elsewhere,   and   thus   they   become    reduced    to   sand. 


WORK    OF   THE    OCEAN.  73 

Every  storm  adds  to  the  shells  of  the  beach  as  well  as 
to  the  shell-sand.  Sand-deposits  are  thus  made  out  of 
shells ;  and  they  keep  growing  and  may  become  of  great 
extent.  They  are  not  deposits  of  quartz  sand,  but  of  calca- 
reous sand.  The  riner  shell-sand  is  swept  out  into  the  shallow 
waters,  and  there  produces  a  finer  deposit.  The  hardening 
of  such  deposits  makes  limestone ;  and  the  shells  that  happen 
to  escape  the  grinding  are  its  fossils.  In  this  way  limestones 
have  been  made  in  all  geological  ages.  Shell-rocks  are  now 
forming  at  St.  Augustine,  Florida,  and  the  limestone  there 
made  is  used  as  a  building  stone. 

In  other  parts  of  tropical  seas  there  are  corals  growing 
profusely  within  reach  of  the  waves,  and  below  to  a  depth 
of  about  150  feet,  with  Mollusks  and  other  kinds  of  sea  life. 
.Many  of  the  corals  become  broken  or  torn  up  by  the  waves 
and  are  carried  to  the  beach,  and  there  ground  up  and  spread 
out  in  beach  deposits  and  off-shore  deposits.  The  shells  of 
the  reef-grounds  add  much  to  the  coral  sands.  These  beds 
of  sand  or  mud  harden  in  the  water,  and  then  become  the 
coral-reef  rock,  a  true  limestone,  similar  to  many  of  ancient 
time. 

Fig.  64  is  a  view  of  a  coral  island,  or  atoll,  of  the  Pacific. 
The  encircling  reef  consists  wholly  of  coral-reef  rock  and 
overlying  coral  sands;  and  the  whole  height  out  of  water  is 
usually  but  1.2  to  20  feet,  or  as  high  as  the  waves  and  the 
winds  can  throw  the  sands.  The  lake  or  lagoon  within  is 
an  inclosed  piece  of  the  ocean,  and  often,  when  a  channel 


74 


MAKING   OF    HOCKS. 


for  entrance  exists,  it  is  an  excellent  harbor  for  shipping. 
Fig.  65  represents  one  of  the  ordinary  high  islands  of  the 
ocean  with  its  shores  bordered  by  coral  reefs.  Such  reefs 


i<;.  64. 


Coral  Island,  or  Atoll. 

are  usually  under  water  except  at  low  tide.  The  inner  reef 
/  is  called  the  fringing  reef,  and  b,  the  barrier,  or  outer  reef. 
At  h  there  is  a  channel  through  the  barrier  opening  to  a 
large  harbor.  Such  reefs  and  islands  exist  in  various  parts 
of  the  tropical  Pacific,  and  also  in  the  East  Indies  and 


High  Island  with  Barrier   (b)   and  Fringing   (f)  Reefs. 

the  West  Indies.  They  border  northeast  Australia  for  looo 
miles. 

5.  Oceanic  Currents. — The  ocean  has  its  system  of  circu- 
lation, or  of  great  currents. 

The  Gulf  Stream  is  one  of  these  great  currents.  Its  waters 
flow  westward  in  the  tropical  Atlantic,  bend  northward  as 
they  pass  the  West  India  seas,  then  flow  northeastward, 
parallel  with  the  North  American  coast  as  far  as  New- 


WOIiK    OF    THE   OCEAN.  75 

foundland,  and  then  gradually  curve  eastward,  toward  Great 
Britain.  Thence  a  part  continues  either  side  of  Iceland  to 
the  Arctic  seas,  from  which  part  returns  as  a  cold  Labrador 
current,  along  the  coast  of  Labrador  and  farther  south; 
another  part  continues  eastward  north  of  Europe  and  Asia. 
This  great  current  moves  but  o  miles  an  hour  where  swift- 
est, and  at  this  rate  only  in  part  of  the  straits  of  Florida. 
Its  average  rate,  parallel  with  North  America,  is  2^  miles 
an  hour;  but  along  the  sides  of  the  continent  it  is  hardly 
felt  at  all  anywhere  along  this  coast,  not  even  in  the  Florida 
straits.  It  hence  gets  no  detritus  from  the  Avear  of  coasts, 
and  is  too  feeble  to  carry  anything  but  the  very  finest  silt. 
The  ocean's  bottom  shows  that  it  receives  almost  nothing 
either  in  this  way  or  from  the  currents  of  great  rivers. 
Local  currents,  made  by  storm  winds  along  shores,  have  been 
far  more  important  transporters  and  distributers  of  detritus 
than  these  oceanic  currents.  When,  however,  the  continents 
were  submerged  a  few  hundred  feet  or  less  in  ancient  time, 
such  currents,  sweeping  over  the  surface,  would  have  done 
much  work  in  Avearing  rocks  and  transporting  detritus,  espe- 
cially in  shalloAv  Avaters  and  along  narroAv  channels. 

6.  Markings  made  over  Sand-flats  and  Mud-flats.  —  Both 
Avaves  and  gentle  currents  raise  ripples  over  the  sands ;  and 
the  ripple-marks  made  by  the  ocean  in  ancient  times  are  often 
preserved  in  the  rocks  (Fig.  66).  Wherever  they  occur  they 
shoAv  that  the  sands  of  Avhich  the  rocks  Avere  formed  Avere 
within  reach  of  Avaves  or  gentle  currents. 


76 


MAKING    OF   ROCKS. 


The  mud  of  a  mud-flat  or  of  a  dried-up  puddle  along  a 
roadside  is  often  found  cracked  as  a  consequence  of  drying; 
and  such  mitdrcracke  are  frequently  preserved  in  sedimentary 
rocks  (Fig.  67).  They  are  of  great  interest  to  the  geologist; 
for  they  show  that  the  layer  in  which  they  occur  was  not  of 
deep-water  origin;  but  beyond  question,  was  exposed,  for  a 
while  at  least,  above  the  water's  surface  to  the  drying  air  or 
sun,  as  mud  is  now  often  exposed  along  a  roadside,  or  over 
the  mud-flats  of  an  estuary.  Such  cracks  become  filled  with 
the  next  deposit  of  detritus,  and  this  filling  has  often  been 


PIGS.  60,  67. 


Ripple-marks. 


Mud-cracks. 


afterward  so  consolidated  as  to  be  harder  than  the  rock  out- 
side ;  and  hence  on  a  worn  surface  the  fillings  of  the  cracks 
often  make  a  network  of  little  ridgelets,  such  as  are  shown 
in  Fig.  67. 


WORK    OF   THE   OCEAN.  77 

Again,  mud-flats  sometimes  have  the  surface  covered  with 
rain-drop  impressions,  after  a  short  shower,  in  which  the 
drops  were  large;  and  many  shales  (rocks  made  of  mud  or 
day)  retain  these  markings 
(Fig.  OS). 

Impressions    of    the    foot- 
prints   or    trails   of    animals, 
also,    and  even    those    of   in- 
sects, are  not  uncommon.  Such 
delicate  impressions  are  pre- 
served,    because     soon     after  Rain-drop  Impressions, 
they   are   made   they    become   covered   with   a   layer  of  fine 
detritus ;  and  after  that  nothing  can  erase  them  short  of  the 
removal  of  the  deposit  itself. 

7.  Great  Extent  of  Deposits  of  Aquatic  Origin.  —  The  rocks 
that  have  been  made  by  fresh  waters  and  the  oceans  are  of 
vast  extent.  They  are  the  sandstones,  conglomerates,  and 
shales  of  the  world;  and  they  include  the  limestones  also. 
The  ocean  has  done  far  the  larger  part  of  the  rock-making. 
In  the  earlier  geological  ages  it  worked  almost  alone;  for 
the  lands  were  very  small,  and  only  large  lands  can  have 
large  rivers  and  river  deposits.  Afterward,  in  the  coal  era, 
there  was  at  least  one  large  delta  or  estuary  on  the  borders 
of  the  American  continent,  —  that  of  the  St.  Lawrence;  and 
in  later  times,  rivers  have  given  important  aid.  During  the 
last  of  the  ages,  after  the  continents  had  reached  ne'arly 
their  present  extent,  and  the  mountains  their  modern  height 


78  MAKING    OF    ROCKS. 

and  numbers,  the  rivers  did  the  larger  part  of  the  distribu- 
tion of  rock  material. 

Sedimentary  rocks  show  that  they  were  formed  through 
the  action  of  water,  often  by  the  rounded  or  water-worn 
pebbles  they  contain,  or  by  the  water-worn  sand,  or  from  a 
resemblance  in  constitution  to  a  consolidated  bed  of  mud 
or  clay ;  by  their  relics  of  aquatic  life,  and  by  the  indica- 
tions of  wave-action  or  current-action  above  pointed  out; 
and  by  their  division  into  layers,  such  as  exist  in  known 
sediments  or  deposits  from  waters ;  and  when  marine,  they 
indicate  it  generally  by  the  presence  of  remains  of  marine 
life. 

(').   The  Work  of  Ice. 

1.  Expansion  on  Freezing.  —  When  Avater  freezes  it  expands. 
If  it   freezes  in   a  pitcher,  the   expansion   is  pretty  sure  to 
break  the  pitcher.     If  it  freezes  in  the  crevice  of   a  rock,  it 
opens    the    crevice;    and   by    repeating   the   process,   winter 
after   winter,  in   the  colder   countries  of  the  globe,  it  pries 
off   and   breaks   apart   rocks,   and   often    makes   a    slope    of 
broken  blocks,  or  talus,  at  the  foot  of  a  bluff.      By  opening 
cracks  in  this  way  it  gives   air  and  moisture   new  chances 
to  do  their  quiet  work  of  destruction. 

2.  Transportation   by  the   Ice    of   Rivers  or  Lakes.  —  When 
water   freezes   over   a   river   it    often   envelops   stones   along 
the  shore;    and  then,  whenever  there  is  a  breaking  up,  the 
ice  with  its  load  of  stones  is  often  floated  off  down  stream; 


AVORK   OF    ICE.  79 

or  if  the  water  of  a  stream  or  lake  rises  in  consequence  of 
a  flood,  the  stones  may  be  carried  farther  up  the  shore  and 
dropped  there,  and  so  make,  in  time,  extensive  accumulations 
of  stones,  large  and  small. 

In  cold  countries  ice  often  forms  thickly  about  the  stones 
in  the  bottom  of  a  stream;  and  as  it  is  lighter  than 
water  it  may  become  thick  enough  to  serve  as  a  float  to 
lift  the  stone  from  the  bottom,  so  that  both  ice  and  stone 
journey  together  with  the  current,  to  become  lodged  some- 
where along  the  shores  or  dropped  to  the  bottom. 

These  are  commonplace  ways  in  which  ice  does  geological 
work.  Its  greater  labors  are  performed  when  it  is  in  the 
condition  of  a  glacier. 

3.  Glaciers.  —  Glaciers  are  broad  and  deep  streams  of  ice 
in  the  great  valleys  of  snowy  mountains  like  the  Alps.  The 
snows  that  fall  about  the  summits  above  the  level  of  per- 
petual snow  accumulate  over  the  high  region  until  the 
depth  is  one  or  more  hundred  feet.  At  bottom  it  is  packed 
by  the  pressure  and  becomes  ice.  Its  weight  causes  the  ice 
to  descend  the  slopes,  of  the  mountains  and  along  the 
valleys,  which  it  fills  from  side  to  side.  The  width  of 
the  ice  of  the  valley  may  be  several  miles;  its  depth  in 
the  Alpine  valleys  is  generally  from  200  to  500  feet. 

The  glaciers  descend  far  below  the  line  of  perpetual  snow 
to  where  the  fields  are  green  and  gardens  flourish;  and  this 
takes  place  because  there  is  so  thick  a  mass  of  ice.  In 
the  Alps  the  glaciers  stretch  down  the  valleys  4500  to 


80 


MAKING    OF   KOCKS. 


r>oOO  feet  below  the  snow-line.     At  (irindelwald  two  glaciers 
terminate  within  a  short  distance  of  the  village. 

The  rate  of  movement  in  the  Alps  in  summer  is  mostly 
between  10  and  20  inches  a  day,  and  half  this  in  winter: 
12  inches  a  day  corresponds  to  a  mile  in  about  14.1,  years. 

>'!(..    till. 


Glacier  of  Zermatt,  or  the  Corner  Glacier. 

Fig.  69.  from  a  sketch  in  Agassiz's  great  work  on  glaciers, 
represents  one  of  tliese  great  ice-streams  or  glaciers  descend- 
ing a  valley  in  the  Moiit.a,  Rosa  region  of  the  Alps.  A 
valley  often  narrows  and  widens  at  intervals,  or  changes  its 
slope  from  nearly  vertical  to  a  gentle  incline,  or  to  a  hori- 


AVOUK    OF    ICE. 


81 


/ontal  surfact'.  The  ice  has  to  accommodate  itself  to  all  these 
variations.  Ou  turning  an  angle  it  Incomes  liroken.  or  lias 
great  numbers  of  deep  -crevasses"  made  through  it,  espe- 
cially on  the  side  opposite  the  angle.  ()n  commencing  a 
rapid  descent,  great  breaks,  or  crevasses,  cross  the  glacier 
from  one  side  to  the  other.  On  again  reaching  a  level 
place,  the  ice  closes  up,  and  the  glacier  loses  nearly  all 
its  crevasses.  The  ice  is  brittle,  and  freezes  together  when 

Kio.   Til. 


Glacial  Scratches  and  Planing. 

the  separated  parts  are  brought  in  contact  again;  so  that. 
as  it  moves,  it  goes  on  breaking  and  mending  itself.  Ice 
•is  plastic;  for  it  may  be  made  into  rods  by  pressing  it 
through  a  hole,  and  will  take  the  impress  of  a  medal;  so 
that  in  this  way  also  it  can  accommodate  itself  to  the 
changing  character  of  the  surface  over  which  it  moves. 
The  steep  upper  slopes  of  the  valley  in  which  a  glacier 

lies    often    send    down    stones    and    earth,    or    avalanches    of 
DANA'S  I.KOI..    >ioi:v — 0 


82 


MAKING    OP    ROCKS. 


ice  and  rocks.  Through  such  falls  a  line  of  earth  and 
rocks  is  commonly  made  along  either  margin  of  the  glacier, 
which  is  called  a  lateral  moraine.  These  moraines  are 
carried  with  the  ice  to  where  it  melts,  and  there  dropped, 
making  a  terminal  moraine.  Other  blocks  are  taken  up  by 
the  sides  and  bottom  of  the  glacier. 

FIG.  71. 


View  on  Roche-Moutonnee  Creek,  Colorado. 

The  rocks  of  the  surface  over  which  a  glacier  has  moved 
are  scratched,  planed,  or  polished,  often  with  great  perfec- 
tion, as  illustrated  in  Fig.  70. 

Ledges  of  rocks  also  are  rounded,  making  \vlmt  are  called 
sheep-backs,  or,  in  French,  roches  montonin'^.  They  are 


WORK    OF    ICE.  83 

most  likely  to  form  where  the  rock  has  some  portions  much 
harder  than  others :  these  hard  portions  can  best  resist 
the  wear  and  they  become  the  sheep-backs.  Fig.  71 
represents  the  roch™  mot/ton IH'PS  in  a  valley  of  the  mountains 
of  Colorado,  —  a  valley  in  the  Rocky  Mountains  leading  up 
to  the  .Mountain  of  the  Holy  Cross,  seen  in  the  distant  part 
of  the  view.  It  is  from  the  Report  of  Dr.  Hay  den  for 
1S7.">.  Xo  glaciers  exist  there  now;  but  once  they  were  of 
great  extent  and  depth.  The  scratching  and  polishing  are 
done  by  the  stones  in  the  bottom  and  sides  of  the  glacier; 
and  these  stones  also,  as  is  natural,  are  planed  off  and 
scratched. 

4.  Icebergs. — In  the  Arctic  regions  the  glaciers  of  Green- 
land, loaded  with  their  moraines,  extend  down  into  the  sea, 
and. the  part  in  the  water  sooner  or  later  breaks  off  and  floats 
away  as  an  iceberg.  These  icebergs  are  carried  south  by  the 
Labrador  current,  and  large  numbers  of  them  in  the  course 
of  a  season  reach  the  Banks  of  Newfoundland.  There  they 
find  the  waters  warmer,  in  consequence  of  the  nearness  of 
the  Gulf  Stream,  and  they  melt  and  drop  their  burden 
of  stones  and  earth  into  the  waters.  It  has  been  sug- 
gested that  the  submerged  Banks  of  Newfoundland  owe 
their  existence  to  the  melting  there  and  consequent  unlading 
of  icebergs. 

It  thus  appears  that  ice  does  geologic  work  (1),  in  the 
act  of  formation,  through  its  expansion;  (2)  as  glaciers,  by 
transporting  over  the  land  earth  and  stones  and  rocks  — 


84  MAKING    OF    ROCKS. 

some  of  the  rocks  as  large  as  ordinary  houses  —  and 
dropping  them  when  the  ice  melts;  (.'>)  by  tearing  off 
rocks  from  the  ledges  over  which  it  may  move,  espe- 
cially where  there  are  opened  seams,  or  joints;  (4)  by 
wearing  deeply  into  the  soft  rocks  over  which  it  mav 
move,  and  scratching  and  polishing  hard  rock ;  (5j  as 
JtoattHf/  ice  or  icebergs,  by  transporting  rocks,  stones,  and 
earth  over  water  from  one  region  to  another;  moreover 
(6)  it  often  makes  temporary  dams  across  valleys,  that  cause 
great  devastation  when  they  give  way;  and  (7),  it  makes 
lakes  in  valleys  and  over  a  glaciated  region  by  the  drop- 
ping of  moraines  to  act  as  dams. 

7.     The   Work   of   Heat. 

The  effects  of  heat  here  considered  are  the  following: — • 

1.  Expansion  and  contraction  from  change  of  temperature. 

2.  The  fusion  of  rocks,  and  their  ejection  through  fissures 
and  volcanic  vents. 

1.    Expansion   and    Contraction. 

Owing  to  the  alternation  each  day  of  sunlight  and  dark- 
ness, the  surfaces  of  exposed  rocks  experience  an  alternate 
heating  and  cooling,  and  therefore  alternate  expansion  and 
contraction.  This  cause,  which  is  sufficient  to  break  the 
solder  of  soldered  metallic  roofs  on  houses,  to  loosen  the 
cemented  blocks  of  a  stone  wall,  and  to  give  a  perceptible 
movement  to  high  stone  towers,  tends  to  start  off  the  grains, 


WORK    OF    HEAT.  85 

and  sometimes  separates  an  outer  layer  from  ban1  rocks, 
especially  when  the  surface  is  weathered.  As  this  agency 
is  at  work  over  the  whole  surface  of  the  earth,  it  is  an 
important  addition,  in  a  quiet  way,  to  the  chemical  work 
of  air  and  moisture,  in  the  making  of  earth  or  gravel  for 
the  formation  of  rock  deposits ;  and  it  has  been  so  ever 
since  the  sun  first  shone  upon  bare  rocks.  A  foot  or  two 
of  soil  is  a  protection  against  this  method  of  degradation. 

Again,  heat  gaining  access  to  rocks  beneath  a  region 
expands  them  and  causes  an  elevation  of  the  surface;  and 
loss  of  heat  produces  a  reverse  effect.  Fractures  may  attend 
such  changes  of  level,  and  also  light  earthquakes. 

2.    Jfakiitf/  of  Rocks  thront/h    Fusion:    Volcanoes. 

1.  Volcanoes.  — igneous  rocks  are  described  on  page  33 
as  having  come  up  in  a  melted  state  to  the  earth's  sur- 
face through  fissures.  In  many  cases  they  have  been 
ejected  at  intervals  from  one  and  the  same  opening  for 
long  periods  of  time. 

When  fissures  are  filled  and  closed  by  one  eruption, 
they  make  dikes  of  igneous  rock,  and  also  one  or  more  beds, 
or  sheets,  if  the  melted  material  flows  from  the  fissure 
over  the  adjoining  region. 

But  when  a  vent  remains  open  for  many  successive  erup- 
tions it  becomes  then  the  center  of  a  true  volcano  or  ti  re- 
mountain.  The  outflows  of  liquid  rock,  and  ejections  of 
volcanic  sand  or  cinders  from  the  vent  on  one  side  or  the 


86 


MAKING    OF    KOCKS. 


other,  produce  a  liill  or  mountain  of  a  form  more  or  less 
nearly  conical.  Fig.  ~U  represents  Mount  Shasta,  one  of  the 
volcanic  mountains  of.  western  North  America,  having  an 
elevation,  according  to  AYhitney,  of  14,440  feet.  It  is  not 
now  in  action,  yet  has  hot  springs  near  its  summit.  It 


Mount  Shasta,   from  the  North,   from  a  photograph  by  Watkins. 

also  represents  well  the  general  form  of  the  great  volcanoes 
of  the  Cascade  range  to  the  north  of  it  in  Oregon,  and 
also  of  those  of  Mexico,  and  of  the  Andes  in  South 
America.  Of  the  latter,  Cotopaxi  is  an  active  volcano 
19,613  feet  in  height,  and  Arequipa  another,  18,877  feet; 


WORK    OF    HEAT.  87 

while   Aconcagua,   of    Chile,  an   extinct   cone,   has   a   height 
of   23,000   feet,   and   is   the   loftiest   peak   in   the   Andes. 

Active  volcanoes,  in  time  of  qniet,  send  forth  only  vapors. 
In  periods  of  eruption,  streams  of  lava  (liquid  rock)  are  poured 
out,  either  over  the  edge  of  the  crater  or  more  commonly  through 
breaks  in  the  sides  of  the  mountain.  At  the  same  time  cinders, 
or  fragments  of  lava,  are  often  thrown  from  the  crater  to  a 
great  height  above  the  volcano,  or  the  finer  particles  called 
ashes,  which  drift  with  the  wind  and  descend  in  showers.  De- 
posits of  wet  ashes  make  a  fragmental  rock  resembling  a 
sandstone  or  breccia,  called  tufa. 

Volcanic  cones  vary  much  in  angle  of  slope.  When 
made  of  dry  cinders  the  angle  is  often  40°  to  42°.  If 
formed  through  the  alternations  of  lavas  and  cinders,  or 
of  tufas,  the  slope  may  be  30°  or  less,  as  in  Figs.  72 
and  73.  Fig.  73  gives  the  slopes  of  the  volcano  of 
Jorullo,  in  Mexico.  Many  of  the 
grandest  volcanoes  of  the  world,  like 
Etna,  and  those  of  Hawaii,  in  the 
Sandwich  Islands,  have  an  exceedingly  gentle  slope,  the 
height  often  only  a  twentieth  of  the  breadth.  Fig.  74  gives 
the  slope  of  Mount  Loa,  FlG  74 

Hawaii.  Its  height  is 
13,675  feet.  Such  cones 
are  made  almost  solely  of  lavas;  and  they  have  so  gentle 
a  slope  because  the  melted  rock  of  the  region  flows  off 
freely,  it  being  of  the  more  fusible  kind,  basalt. 


88  MAKING    OF    ROCKS. 

The  eruptions  of  volcanoes  are  owing  mainly  to  the  waters 
that  gain  access  to  the  fires.  The  rains  of  the  region  pro- 
duce underground  streams  and  trickling  waters  that  descend 
and  pass  into  the  melted  rock,  there  to  be  changed  to  vapor. 
Sea-water,  when  volcanoes  are  near  or  in  the  ocean,  some- 
times presses  its  way  in,  or  gains  access  suddenly  through 
fractures.  The  vapor  penetrating  the  liquid  mass  expands 
the  whole,  causing  it  to  rise  in  the  vent.  With  the  increas- 
ing height  of  the  column  of  melted  rock  in  the  mountain, 
the  vapors  become  more  active.  The  pressure  from  the 
high  liquid  column,  and  from  the  vapors,  breaks  the  moun- 
tain, and  the  lavas  run  out,  devastating  the  country,  it 
may  be,  for  a  score  of  miles  or  more.  When  the  sea 
gains  sudden  access  to  a  volcanic  vent,  the  eruption  is  ac- 
companied with  violent  qxiakings  of  the  mountain.  Every 
few  years  the  country  011  one  side  or  another  of  Vesu- 
vius is  deluged  with  the  fiery  rock,  cultivated  fields  are 
buried,  and  not  unfrequently  villages  are  destroyed.  Pom- 
peii and  Herculaneum  were  buried  beneath  the  cinders 
of  an  eruption  that  took  place  in  the  year  70;  and  since 
then  several  streams  of  lava  have  flowed  down  over  Hn- 
culaneum,  adding  to  the  depth  at  which  it  is  buried. 

Mount  Loa,  on  Hawaii,  has  had  eight  great  eruptions 
through  fissures  in  the  sides  of  the  mountain  since  1840. 
There  is  a  summit  crater  at  a  height  of  13,7(>5  feet,  and 
another,  still  larger,  called  Kilauea,  nearly  -1000  feet  above 
the  sea.  The  map,  Fig.  7">,  shows  the  courses  of  the  erup- 


WORK    OF    HEAT. 


80 


tions.     Mount  Kea  is  another  volcanic  mountain,  as  high  as 
Loa,  and  another,  Mount  Hualalai,  is  over  8000  feet  high. 

FIG.  "5. 


,    •*,  TAELE  LANDK/000    ,O      ,0.00    --.....«>>•     v-g" .«  .  -^     : 

1      -,.iiSc5.^'  ^-f.f,e"s*-^-c^;>- '^"  •;"-" 


HAWAII 

F.ROM  THE 

GOVEBJOTENT  MAP 


The  liquid  rock  comes  up  from  some  deep-seated  iire- 
region. 

Volcanic  mountains  are  very  numerous  along  the  Andes; 
in  (,'entral  America  and  Mexico;  in  Oregon  and  Washington 


90  MAKING    OF    ROCKS. 

from  Mount .  Shasta  to  Mount  Baker  and  beyond;  in  the 
Alaska  archipelago  on  the  north;  all  along  the  west  side 
of  the  Pacific  through  Japan  and  the  East  Indies ;  south- 
ward in  the  New  Hebrides,  Xew  Zealand,  and  in  Antarc- 
tic regions.  Thus  the  Pacific,  the  great  ocean  of  the 
globe,  is  girt  with  volcanoes,  besides  having  many,  though 
mostly  extinct  cones,  over  its  surface.  The  Atlantic,  in 
contrast  with  it,  has  none  on  its  borders,  except  in  the  Gulf 
of  Guinea  on  the  coast  of  Africa,  and  in  the  West  Indies ; 
and  but  few  over  its  interior. 

2.  Hot  Springs;  Geysers.  —  Hot  springs  often  make  deposits 
of  silica  on  their  borders,  owing   to  the  silica  the   heat  has 
enabled  the  waters  to  take  up   from  the  rocks  with  which 
they   are   in   contact.     Such   springs   sometimes   throw   their 
waters   in  jets  at  longer  or  shorter   intervals,  and   they  art- 
then  called  geysers.     One  of  the  geysers  of  the  Yellowstone 
Park,  in  the  Rocky  Mountains  (where  there  are  great  num- 
bers  of  them),  is    represented   in   action    in    Fig.    7(5,   taken 
from  Hay  den's  Report  for  1873.      It  throws  the  water  to  a 
height   of  200   feet   or   more.      The  geysers  of  Yellowstone 
Park  are  mostly  about  the  Fire-hole  River,  a  fork  of  Madison 
River,  and  near  Shoshone  Lake,  the  head  of   Snake    River, 
and  not  far  from  the  head  of  the  Yellowstone.     The  number 
of  hot  springs,  hot  lakes,  and  geysers  in  the  Park  has  been 
stated  to  be  not  less  than  10,000. 

3.  Solfataras.  —  Solfataras  are  feebly  active  volcanic  vents, 
where  vapors  issue  and  sulphur  is  deposited. 


Ki.:. 


Beehive  Geyser  in  Action. 


92  MAKING    OF    ROCKS. 

8.    Solidification  and  Metamorphism. 

1.  Solidification.  — The  two  most  common  methods  of 
solidification  of  fragmental  deposits  are  (1)  by  means  of 
lime  carbonate  (strictly  bicarbonate) ;  and  (-)  by  silica. 

All  waters  contain  some  carbonic  acid  gas.  The  rains 
take  it  from  the  atmosphere  and  carry  it  down  to  the  soil, 
lakes,  and  oceans ;  and  the  respiration  of  animals  and  the  de- 
composition of  organic  matter  are  other  sources.  When  calca- 
reous sands,  as  those  of  coral,  or  shells,  or  powdered  lime- 
stone, are  wet  by  carbonated  waters,  these  waters  take  up 
some  of  the  lime  carbonate  in  the  form  of  bicarbonate;  and 
this  lime  carbonate  they  deposit  among  the  grains,  as  the 
water  evaporates,  and  the  excess  of  carbonic  acid  is  exhaled, 
cementing  them  together.  The  process  goes  on  also  under 
Avater  where  there  is  no  evaporation,  as  in  the  conversion 
of  closely  compacted  coral  sands  and  shell  sands  below 
tide  level  into  coral  limestone  or  shell  limestone. 

\Vaters  containing  a  little  soda  or  potash  in  solution 
will  dissolve  the  silica  of  organic  relics,  such  as  sponge 
spicules  and  ])iatoms,  even  when  cold,  and  more  readily 
when  hot.  The  masses  of  flint  or  hornstone  found  in  some 
beds  of  chalk  and  many  other  kinds  of  limestone  were 
made  out  of  such  relics  in  the  sea  through  their  partial 
solution  and  consolidation,  and  generally  without  heat  above 
the  ordinary  temperature. 

Hot  waters,  as   explained  on  page  18,  are  very  likely  to 


SOLIDIFICATION    AND   METAMORPHISM.  93 

hold  silica  in  solution  ;  and  if  so,  such  waters,  as  they  cool, 
will  deposit  the  silica  among  the  grains  of  quartz  sand, 
or  pebbles,  and  produce  the  firmest  of  rocks.  Oxide  of  iron, 
also,  is  sometimes  a  cement,  even  of  common  gravel  beds. 

Some  of  the  oldest  of  sandstones  and  shales  are  still 
soft,  or  feebly  consolidated,  because  not  furnished  with  any 
cementing  material. 

2.  Metamorphism.  —  Metamorphism,  like  metamorphosis, 
means  change  of  some  fundamental  kind.  In  geology  it 
may  be  change  only  in  texture ;  but  it  includes  also  changes 
in  the  nature  or  composition  of  the  minerals  of  a  rock.  It 
is  change  produced  when  rocks  are  subjected  to  heat  with 
moisture,  for  heat  cannot  be  distributed  through  the  rocks 
without  the  agency  of  moisture  to  become  steam  and  so  give 
it  diffusion. 

When  melted  rock  ascends  along  a  fissure,  it  heat  a  the 
walls,  and  the  effects  of  the  heat  are  in  part  metamorphic 
effects.  Sometimes  it  only  consolidates  the  rocks.  But,  besides 
this,  if  a  limestone  is  intersected  by  the  fissure,  the  heat  may 
crystallize  the  limestone  to  a  depth  of  some  inches  or  feet, 
converting  thereby  the  compact  rock  into  one  of  crystalline 
texture  looking  like  coarse  loaf  sugar.  This  crystallization 
is  one  kind  of  metamorphism. 

It  may  also  make  epidote  or  garnet,  or  some  other  mineral, 
in  the  wall  of  the  fissure,  if  the  elements  of  the  mineral  are 
present  in  any  of  the  intersected  rocks.  This  chemical  change 
is  a  second  kind  of  metamorphism. 


94  MAKING    OF    ROCKS. 

Other  examples  occur  sometimes  about  hot  springs.  The 
waters  of  geysers  deposit  a  large  amount  of  silica  in  the  form 
of  opal,  making  opal  basins  for  themselves  to  play  in,  and 
spreading  the  opal  widely  over  the  region  around.  They 
also  produce  the  petrifaction  of  wood,  changing  the  trunk  of 
a  tree  into  silica. 

The  above  cases  are  examples  of  load  metamorphism ; 
that  is,  metamorphic  change  in  a  rock  adjoining  a  I»<-<it 
source  of  heat. 

Besides  cases  of  local  change,  metamorphism  has  gone 
forward  sinmltaiieously  through  rock-formations  thousands 
or  hundreds  of  thousands  of  square  miles  in  area,  and  a 
score  or  more  thousands  of  feet  thick ;  the  whole  having 
been  heated  up  to  a  high  temperature  at  one  time  through 
some  subterranean  method.  In  this  grand  way,  changes  (1) 
in  crystallization  and  (2)  in  chemical  composition  have  been 
produced  on  a  vast  scale.  This  is  regional  metamorphism. 

Limestone  formations  have  been  rendered  crystalline 
through  the  whole  of  a  heated  region.  A  sandstone,  made 
of  granitic  sand,  has  received  a  new  crystalline  finish  to  its 
grains,  and  has  become  granite  again,  or  if  retaining  its 
stratification,  it  has  become  the  related  rock,  gneiss. 

Further,  the  minerals  occurring  as  impurities  in  various 
rocks  subjected  to  the  heating  have  undergone  more  or  less 
change  in  composition,  and  have  been  converted  into  crystals. 
A  limestone  containing  impurities  of  clay,  sand,  iron  oxide, 
and  other  materials  has  come  from  the  great  laboratory  of 


SOLIDIFICATION    AND    METAMORPHISM.  95 

nature  full  of  crystals  of  different  kinds  and  colors ;  and 
so  it  has  been  with  other  rocks.  For  vapor  or  steam  at  a 
high  temperature  has  great  decomposing  and  recomposing 
power.  Laboratory  experiments  have  made  by  its  means 
crystals  of  various  minerals.  Moreover,  many  of  the  world's 
finest  gems  —  its  emeralds,  sapphires,  rubies  —  are  in  part  of 
in  etam  orphic  origin. 

As  the  heat  concerned  may  be  more  or  less  great,  and 
the  rocks  subjected  to  the  process  have  been  of  all  kinds, 
from  better  shales  to  sandstones  and  conglomerates  of  various 
composition,  and  also  to  limestones,  the  diversity  of  re- 
sults is  very  large.  .Some  of  the  kinds  of  metamorphic 
rocks  are  mica  schist,  liydromica  schist,  hornblende  schist, 
chlorite  schist,  as  well  as  gneiss,  and  part  of  the  granite 
of  the  world.  The  heat  of  metamorphism  was  generally 
below  that  required  for  the  fusion  of  the  rocks ;  for  their 
stratification  is  generally  retained.  For  example,  the  layers 
of  mica  schist  and  gneiss  usually  correspond  with  the 
bedding  of  the  sandstone  or  shale  out  of  which  they  were 
made.  But,  in  some  eases,  the  heat  was  sufficient  to  soften 
the  rock,  and  then  the  planes  of  stratification  were  oblit- 
erated, making  granite  instead  of  gneiss,  —  granite  differ- 
ing from  gneiss  only  in  the  absence  of  anything  like 
stratification. 

In  cases  of  regional  metamorphism  the  heat  has  been 
derived  from  profound  movements  that  were  in  progress 
in  the  rocks.  The  great  region  was  in  the  process  of 


0(1  MA  KINO    OF    KOCKS. 

mountain-making;  the  upturning  and  flexing  of  rocks  many 
thousands  of  feet  thick  were  going  forward  in  order  to 
make  a  range  of  mountains  out  of  them.  The  friction 
produced  by  the  vast  movements  was  the  chief  source  of 
the  heat.  Some  heat,  however,  was  the  heat  of  the  earth's 
interior,  for  it  has  been  found  that  in  descending  below 
the  earth's  surface,  after  passing  the  level  which,  has  con- 
stantly the  mean  temperature  of  the  place,  the  temperature 
increases  about  1°F.  for  every  /"><)  or  <>(>  feet  of  depth. 

As  the  heated  region  has  often  been  hundreds  of  miles 
long  and  thousands  of  square  miles  in  area,  and  the 
temperature  for  the  most  part  over  1000°  F.,  it  is  not  sur- 
prising that  crystallization  and  other  changes  of  great  rock 
formations  should  have  been  a  result.  The  larger  part  of 
the  rocks  of  New  England  and  of  much  of  the  Atlantic 
border  to  the  south,  of  Canada  to  the  north,  of  the 
northern  part  of  New  York,  Michigan.  Wisconsin,  and 
Minnesota,  of  large  areas  in  the  summit  region  of  the 
Rocky  Mountains,  and  over  the  Pacific  slope,  are  meta- 
morphic  rocks. 

'.).    Veins   and   Ore   Deposits. 

1.  General  Characters.  —  Veins  fill  fissures  in  the  earth's 
rocks.  They  may  cut  across  the  rocks  vertically  or  nearly 
so,  as  in  Fig.  77  (act,  bb) ;  or  be  much  inclined,  as  in 
Fig.  78.  The  fissures  may  be  regular,  with  nearly  paral- 
lel Avails  for  long  distances ;  but  they  commonly  vary  greatly 


VEINS  AND   OKE   DEPOSITS. 


97 


ill    width   along   their   course.     The    width    may    be   that   of 
paper,  or  of  hundreds  of  feet. 

Besides  veins  interaectimj  the  strata,  there  are  others  of 
large  size  as  well  as  small,  that  are  the  fillings  of  oniony* 
between  the  layers  of  a  laminated  or  schistose  rock,  as 

FIGS.  77,  7N 


Intersecting  Veins,  •/,  </'.  h. 

illustrated  in  Figs.  79  to  81.  In  Fig.  <S1  the  openings  are 
but  a  small  fraction  of  an  inch  in  thickness,  and  occur 
between  successive  layers. 

Fu;s.  79-81. 


Interlaminating  Veins. 


The  above  figures  represent  simple  veins.  Many  veins 
are  made  up  of  two  or  more  layers  parallel  to  the  walls. 
Such  veins  are  called  landed  veins,  because  they  appear 


DANA'S  UKOI..  STOKY —  7 


MAKING    OF    MOCKS. 


banded  in  a  transverse  section.     In  Fig.  <S2  there  are  two  such 
layers,  one  attached  to  each  wall.     Between  the  layers  there 
r,G  go.  is  often  a  layer  of   ore  ;    and   in  other 

cases,  wider  spaces  occur  at  intervals 
containing  ore,  as  represented  in  Fig.  S2. 
When  a  vein  contains  ore,  it  is  called 
by  miners  a  lode. 

Veins    are    often   faulted.      Fig.    78 

represents   a  faulted   vein.     The   fault 

.       ,, 

is   the  consequence   or   a   fracture  and 


Banded   Quartz    Vein. 


a  lateral  shove  along  it  after  the  vein  was  made.  Such 
shoves  or  displacements  may  be  for  a  few  feet,  or  for 
hundreds  or  thousands  of  yards,  making  it  very  difficult 
to  find  the  continuation  of  the  vein. 

2.  Material  of  Veins.  —  Veins  often  consist  wholly  of  quartz  ; 
others  are  of  coarse  granite,  or  some  related  rock.     Some  are 
made  of  ore  alone;  but  often  the  ore  is  associated  with  other 
materials.     The    most    common   vein-stones,   or    associates    of 
ores,  are   quartz,  calcite,  dolomite,  barite,  and  fluorite.     Dif- 
ferent ores  often  occur  in  the  same  vein,  and  sometimes  each 
makes  a  separate  layer  in  a  banded  vein. 

3.  Formation  of  Veins.  —  Fissures,  the  necessary  prelude  to 
vein-making,  are,  to  a  great  extent,  a  result  of  the  upturning 
and  flexing  or  wrenching  movements  incidental  to  mountain- 
making.     Hence  veins   are   most  numerous  in    mountain  re- 
gions or  regions  of  upturned  rocks  ;   but  many  occur  in  the 
outskirts  of  such  regions. 


VEINS   AND   ORE   DEPOSITS.  99 

The  making  of  ordinary  veins  lias  required  heat.  The 
material  has  not  come  up  into  the  fissure  in  a  melted  state, 
as  in  the  making  of  dikes,  but  has  entered  gradually  by 
the  sides,  or  from  below,  in  solution  in  hot  water.  The 
vein-material  has  been  deposited  first  against  the  walls ;  and 
afterward  the  central  part  was  filled,  as  illustrated  in  Fig. 
S2;  and  if  consisting  of  more  than  two  bands,  each  band, 
after  the  deposition  of  the  outer  one,  has  been  added  succes- 
sively in  the  unfilled  center. 

4.  Sources  of  Heat  involved  in  Vein-formation.  —  There  are 
two  classes  of  veins  differing  in  the  source  of  heat. 

1.  Vein*  in  HHikiiif/  tr/ii,-Jt  tlie  heat  concerned  teas  produced,  to 
<i  larye   extent,  by  tlie  friction    attending   mountain-making.  — 
The  heat,  in  this  case,  was  the  same  that  produced  the  meta- 
morphism    of    the    rocks,   and    this    latter    work    may    have 
been   still   in   progress.      Such    veins   intersect    metamorphic 
rocks.      Quartz    veins    are    most    abundant   in    the    rocks    of 
feeble     metamorphism,    as    chlorite    schist    and    hydromica 
schist,  because  silica  solutions  may  be  made  at  a  low  tem- 
perature; and  granite  veins  occur  chiefly  in  mica  schist  and 
gneiss. 

Gold  is  obtained  from  quartz  veins,  where  it  exists  mostly 
in  minute  scales,  often  with  lead  ore  and  pyrite;  it  was 
taken  into  the  vein  at  the  same  time  with  the  quartz  from 
the  outside  rocks  of  the  region. 

2.  Veins  in  nHikimj  irhich  the  heat  teas  supplied  by  igneous 
eruptions.  —  Great  igneous  eruptions  occurred  in  early  geolog- 


100  MAKING    OF   ROCKS. 

ical  time,  in  the  region  of  Lake  Superior,  and  especially 
along  the  south  side  of  the  lake  at  Keweenaw  Point;  and 
owing  to  the  heat  of  the  melted  rock,  copper  was  brought 
up  by  the  sides  of  it,  as  it  ascended,  and  partly  within 
it;  and  thus  the  rich  'mines  of  native  copper  in  that 
region  were  made.  It  is  probable  that  the  copper  was 
derived  from  veins  of  copper  ore  that  existed  somewhere 
deep  below  in  the  rocks  intersected  by  the  fissures. 

In  many  silver-mining  regions  of  the  Rocky  Mountains, 
where  the  ore  is  derived  in  like  manner  from  the  deeper 
parts  of  the  fissure  walls,  the  fissure  in  its  upper  part 
intersects  limestone  strata ;  and  as  limestone  is  easily  eroded 
by  mineral  or  acid  vapors,  great  caverns  were  made  in  the 
limestone  by  such  vapors,  and  at  the  same  time  the  ores 
were  deposited  in  these  cavities  or  caverns.  The  ores  are 
often  distributed  also  along  the  walls  of  a  fissure,  but  in 
general  the  harder  or  more  enduring  rocks  of  the  walls  get 
none  of  it. 

In  Missouri,  northern  Illinois,  and  southern  Wisconsin, 
there  are  great  deposits  of  lead  ore  or  galenite  in  cavities 
of  different  limestone  formations,  much  resembling  those  of 
the  Rocky  Mountain  mines  just  described.  But  as  no  evi- 
dence has  yet  been  obtained  to  show  that  the  deposits  are 
connected  below  with  igneous  rocks,  the  ore  is  supposed  to 
have  been  brought  into  the  cavities  from  above.  The  cavities, 
or  the  minerals  they  contain,  show  that  they  were  enlarged 
by  the  mineral  solution,  produced  through  the  oxidation  of 


VALLEYS   OF    EROSION.  101 

the  ores,  as  they  much  resemble  those  of  many  silver  mines 
in  the  Rocky   Mountains. 

II.     MAK1XC    OK    VALLEYS. 

Valleys  are  made  (1)  commonly  by  <<r<>xion  by  the  streams 
of  the  land;  (H)  by  >ij>liftiti</K  or  jlt-surcx  of  rocks  making 
mountains  and  leaving  troughs  or  low  regions  between  the 
mountains  as  valleys ;  (3)  through  fractures  of  the  earth's  crust. 

1.    Valleys  of  Erosion. 

Slopes  of  sand  or  gravel  are  sometimes  deeply  gullied  by 
the  heavy  rains  of  a  single  day,  or,  in  geological  language, 
deeply  eroded,  or  eaten  out,  as  this  word  means.  This  work 
of  the  rains  often  gives  a  very  exact  model,  on  a  small 
scale,  of  the  valleys  and  ridges  of  mountain  regions.  The 
gully,  or  little  valley,  has  often  (1)  a  precipice  at  its  head; 
(2)  little  waterfalls  along  the  steep  part  of  its  course,  wher- 
ever there  was  a  harder  layer  of  sand ;  (3)  a  narrow  bottom 
with  steeply  sloped  sides ;  but  at  the  foot  of  the  hill,  where 
the  surface  is  nearly  horizontal,  a  broad  and  flat  bottom  of 
sand  laid  down  by  the  spreading  waters.  And  the  ridgelets 
between  the  little  valleys  have  often  a  broken,  knife-edge 
summit  in  their  upper  part,  and  are  broader  below.  The 
reader  should  study  carefully  the  first  gullied  slope  of  this 
kind  that  he  may  meet  with,  for  it  will  be  a  study  of  val- 
ley-making the  world  over.  Only  a  single  night's  rain  may 
have  sufficed  to  make  the  little  valleys  and  ridgelets  of  the 


102  MAKING   OF    VALLEYS. 

sand  slope,  because  the  sand  was  not  firmly  consolidated.  But 
if  the  rocks  be  ever  so  hard,  they  yield  in  the  same  way,  and 
with  time  enough,  the  same  forms,  on  the  scale  of  the  grand- 
est mountain  region  of  the  world,  have  resulted.  Many  of  the 
river-valleys  of  North  America,  and  of  other  continents,  illus- 
trate this  action  of  running  water.  Watkins  Glen  near 
Heneca  Lake,  Trenton  and  Niagara  Falls  in  central  and  west- 
ern New  York,  the  Valley  of  the  upper  Mississippi,  and  the 
canon  of  the  Colorado,  afford  examples.  The  character  of  the 
valleys  and  ridges  will  depend  much  on  the  hardness,  struc- 
ture, and  position  of  the  rocks.  When  the  beds  are  nearly 
horizontal,  precipices  and  waterfalls  are  most  common. 

The  Colorado  River  of  western  North  America,  runs  for 
200  miles  through  a  gorge  or  canon  with  vertical  walls  of 
rock  in  many  places  over  3000  feet  high.  The  sketch  in  Fig. 
83,  from  a  photograph  obtained  by  Powell's  expedition,  is  a 
view  of  a  portion  of  this  canon  between  the  Paria  and  the 
mouth  of  Little  Colorado,  called  Marble  Canon.  The  walls  in 
the  distant  part  of  the  view  have  a  height  of  3500  feet,  and 
consist  of  limestone,  whence  its  name.  In  other  parts  of 
the  Colorado  canon  there  are  various  kinds  of  strata,  and  in 
some  places  the  cut  has  been  made  deep  into  the  underlying 
granite,  and  all  is  the  work  of  the  river.  Another  scene 
from  the  canon  is  shown  in  Fig.  11,  on  page  36.  The  waters 
have  a  rapid  and  often  plunging  flow,  owing  to  the  slope,  and 
carry  along  pebbles  and  stones,  and  the  stones  and  sand  have 
been  efficient  agents  in  the  erosion.  But  to  wear  out  so  wide 


VALLEYS    OF   EROSION. 


103 


and  deep  u  channel  a  long  period  of  time  was  required.  Above 
the  gorge,  some  miles  back  from  the  river,  the  horizontal  rocks 
are  piled  up  to  a  still  greater  height,  reaching  in  some  places  a 
level  8500  feet  above  that  of  the  bed  of  the  stream ;  and  these 
piles  of  strata  standing  in  separate  ridges,  sometimes  in  the 

FIG.  88. 


Marble  Canon,  on  the  Colorado. 

form  of  pinnacles,  castellated  structures,  and  table-topped 
mountains,  are  parts  of  great  rock-formations  that  once  spread 
across  the  wide  region.  They  show  that  erosion  has  carried 
away  the  larger  portion  of  these  upper  rocks;  and  that  the 
mountains  and  pinnacles  are  merely  the  remnants  left. 


104  MAKING    OF    VALLEYS. 

The  ocean  lias  aided  in  the  degradation  of  the  land  where 
it  was  partly  submerged;  but  it  could  not  have  cut  out  a 
gorge  or  canon;  for  the  work  of  the  ocean  is  to  wear  oif 
headlands,  form  sand-flats  or  beaches  along  coasts,  and  till 
up  bays ;  not  to  cut  channels  into  a  coast  and  make  deep 
valleys.  The  ocean  has  done  but  little  valley-making,  and 
only  that  of  the  broadest  kind,  \vhen  its  wide  currents 
swept  over  a  submerged  continent.  The  gorging  of  moun- 
tains and  plains  it  lias  left  to  the  running  waters  of  the 
land,  aided  in  some  cases  by  glacier-ice  (page  70). 

-,  Valleys  made  by  the  Upheaval  of  Mountains. 
The  wide  Mississippi  Valley  is  a  depression  between  the 
Rocky  Mountains  on  the  west  and  the  Appalachians  on  the 
east.  The  making  of  these  mountains  was  the  making  of  the 
valley.  The  Connecticut  and  Hudson  Rivers  occupy  depres- 
sions that  were  probably  made  by  uplifts  either  side  of  them. 
The  Adirondacks  are  among  the  oldest  of  mountains.  Long 
after  these  the  Taconic  Mountains,  along  the  western  border  of 
New  England,  were  made ;  and  when  raised,  the  valley  in 
which  Lake  Ohamplain  lies  was  a  low  region  between  them. 
Again,  the  valley  of  the  Sacramento  originated  in  the  making 
of  the  Sierra  Nevada  on  one  side,  and,  later,  the  Coast  ranges 
on  the  other.  All  the  continents  afford  similar  examples. 

3.   Valleys  made  by  Fractures  of  the  Earth's  Crust. 
(1)  A  great  fissure  in  a  volcanic  mountain  opened   for  the 
eject  ion  of  lavas  has  sometimes  been  left,  after  the  eruption 


IGNEOUS    EJECTIONS.  105 

ceased,  as  a  deep  valley.  (2)  Great  regions  have  subsided 
in  consequence  of  subterranean  movements,  leaving  valley-like 
depressions.  (3)  Profound  fractures  have  taken  place  in  con- 
nection with  mountain-making,  leaving  sometimes  open  rents, 
as  narrow  valleys  or  gorges. 

But,  notwithstanding  the  frequency  of  fractures,  there  are 
few  valleys  over  the  earth  that  can  be  pointed  to  as  made 
in  this  way.  Fractures  have  sometimes  determined  the 
courses  of  streams;  but  the  stream,  thus  guided  in  its 
original  course,  has  afterward  itself  carried  forward  its 
work  of  erosion,  and  made  the  great  valley  in  which  it 
flows. 

III.     MAKING    OF    MOUNTAINS,   AND    THE   ATTENDANT 
EFFECTS. 

There  are  three  prominent  methods  of  producing  moun- 
tain elevations. 

1.    Mountains  made  by  Igneous   Ejections. 

Mountains  have  been  made  by  igneous  ejections,  especially 
by  those  of  volcanic  vents,  as  explained  on  page  85.  Thou- 
sands of  square  miles  over  the  western  slope  of  the  Rocky 

• 

Mountains  have  been  covered  by  igneous  rocks,  and  in 
Oregon  they  have  a  thickness  of  more  than  4000  feet; 
and,  besides,  they  form  cones  there,  whose  summits  are 
10,000  to  14,440  feet  above  the  sea.  The  loftiest  peak  of 
the  Andes,  2.°>.000  feet  high,  as  already  stated,  and  numer- 


10()  MAKING     OF     MOUNTAINS. 

ous  others  in  that  chain,  were  made  by  volcanic,  action. 
Mount  Etna,  in  Sicily,  is  nearly  11,000  feet  high;  two 
volcanic  mountains  of  Hawaii  are  nearly  14,000  feet  high ; 
Ori/aba,  in  Mexico,  18,200  feet. 

This  is  the  least  important  of  the  methods  by  which  moun- 
tains have  been  formed. 

2.  Mountains  and  Hills  produced  by  the  Erosion  of  Elevated  Lands. 

In  all  mountain  regions  the  lofty  summits  and  ridges  have 
been  shaped  out  mainly,  as  already  explained,  by  running 
water,  and  such  heights  are  therefore  examples  of  the  results 
of  erosion  on  elevated  lands.  I  Jut  the  mountain-making  is 
more  completely  the  work  of  erosion  when  a  region  of 
horizontal  rocks,  which  was  a  lofty  plateau  when  first 
raised,  has  undergone  long  erosion.  Owing  to  the  height, 
perhaps  several  thousand  feet,  the  torrents  which  the  rains 
make  and  feed  have  a  steep  descent,  and  therefore  great- 
eroding  power;  and  ultimately  such  a  plateau  has  often 
been  reduced  to  a  region  of  profound  valleys  and  precip- 
itous ridges.  The  elevations  described  on  page  10.°>  as  the 
remnants  of  a  great  rock-formation,  are  examples  of  moun- 
tain sculpture  of  this  kind.  These  remains  are  battlemented 
heights,  temples  of  mountainous  dimensions,  towers,  and 
columns.  The  Oatskills  are  a  group  of  high  summits  ,'JOOO 
to  4000  feet  above  the  sea  level,  carved  by  running  water 
out  of  an  elevated  region  of  nearly  horizontal  rocks.  Such 
examples  are  common  over  the  world.  For,  in  the  changes 


EROSION    OF    ELEVATED    LANDS. 


107 


of  level  which  the  earth's   crust  has  undergone,  areas  have 
often    been   lifted   without   much   disturbance  of   the  beds. 

The  elevations  have  often  a  broad  cap  of  harder  rock  at  top, 
and  if  of  much  breadth  they  are  called  mesas,  or  table-moun- 
tains, from  the  Spanish  mesa,  a  table.  Many  mesas  over  the 
Pacific  slope  have  at  top  thick  sheets  of  some  igneous  rock, 
Avhich  has  served  to  protect  the  rock  below  from  wear. 

Examples  of  monumental 
forms  on  a  small  scale  oc- 
cur iu  Colorado,  and  have 
given  the  name  of  Monu- 
ment Park  to  the  region. 
Fig.  (S4  is  a  sketch  of  one 
of  its  scenes,  from  Hayden's 
Iveport  for  l!S7o.  Such 
effects  of  erosion  may  have 
been  produced  mainly  by 
rains  and  running  water; 
but  they  are  in  part  due 
to  the  winds ;  to  the  quiet  Scene  in  M°n«ment  Park,  Colorado. 
work,  chemical  in  nature,  of  air  and  moisture ;  to  the  alternate 
heating  and  cooling  of  the  surface  in  consequence  of  the  daily 
changes  of  temperature ;  and  in  frosty  regions,  or  where  the 

winters  are  cold,  to  the  freezing  of  moisture  over  the  surface. 

• 

Over  undisturbed  regions  of  Tertiary  and  Quaternary  for- 
mations of  moderate  elevation,  erosion  has  often  reduced  the 
once  level  surface  to  a  collection  of  hills.  In  some  parts  of 


108  MAKING    OF    MOUNTAINS. 

the  eastern  slope  and  summit  of  the  Kocky  Mountain  region 
the  Tertiary  is  worn  into  a  labyrinth  of  valleys  and  variously 
shaped  ridges,  needles,  and  table-like  elevations. 

This  mountain-making  by  erosion  is  an  external  sculpturing 
of  the  earth's  surface,  and  not  true  mountain-making. 

3.    Mountains  made  by  Upturnings  and  Flexures  of  Rocks,  and 
Bendings  of  the  Earth's  Crust. 

Mountain  ranges  have  been  made,  for  the  most  part,  through 
bendings  of  the  earth's  crust,  and  the  upturning,  flexing,  and 
faulting  of  the  rocks. 

1.  Upturned  Rocks.  —  The  layers  of  stratified  rocks  were  orig- 
inally, with  small  exceptions,  horizontal,  this -being  the  posi- 
tion which  layers  of  sediment  usually  have  when  forming. 
Now,  very  commonly,  they  are  more  or  less  upturned.  Some- 
times the  angle  of  inclination  is  small ;  but  in  most  mountain 
regions  the  beds  are  steeply  inclined,  and  often  are  ver- 
tical or  nearly  so.  In  the  study  of  the  inclined  position  of 
strata  the  geologist  studies  the  origin  of  mountains. 

The  inclination  of  the  beds  below  a  horizontal  plane  is  called 
the  dip;  and  the  horizontal  direction  at  right  angles  to  the  >li/> 
is  the  strike.  When  the  roof  of  a  house  slopes  in  opposite  direc- 
tions from  a  horizontal  ridge-pole,  the  angle  of  slope  or  the 
pitch  of  the  roof  corresponds  to  the  dip;  and  the  direction  of 
the  ridge-pole,  to  the  strike. 

Some  of  the  positions  of  upturned  rocks  are  shown  in  the 
following  figures.  Fig.  85  represents  a  ledge  of  rocks  pro- 


UPTUJININGS    AND    FLEXURES    OF    ROCKS. 


109 


jecting  above  the  ground  ;  dp  is  the  direction  of  the  dip,  aiid 
st  that  of  the  strike.  Fig.  8G  represents  a  portion  of  the  coal- 
formation  with  stumps  of  trees  rising  out  of  the  coal-beds, 


Fins.  S5,  S6. 


Upturned  Strata. 

which  have  lost  their  vertical  position  because  of  the  upturn- 
ing of  the  strata. 

2.    Flexures. —  Figs.  87-91  represent  flexures  or  folds  of  the 
strata,  such  as  are  of  common  occurrence.     The  folds  in  a 


FIGS.  87-91. 


Flexed  or  Folded  Strata. 


mountain  region  are  sometimes  many  miles  in  span ;  and  often 
one  arch  rises  beyond  another.  The  Appalachians  and  Jura 
Mountains  are  full  of  examples. 


110  MAKING     OF    MOUNTAINS. 

The  upward  bend  (at  ax  in.  Figs.  87-90)  is  called  an  a  nfi- 
cline,  from  the  Greek  signifying  inclined  in  opposite  directions; 
and  the  downward  bend  (at  a'x')  a  syncline,  meaning  inclined 
together.  ax,  a'x'  are  the  positions  of  the  axial  planes  of  the 
folds,  and  the  intersections  of  these  planes  with  the  surface  of 
the  strata  are  the  axes  of  the  folds;  ax  an  «iiti<-l/n<il  «xi>t,  and 
a'x'  a  syiH-Hiuil  ".'•/*.  In  Fig.  91  three  folds  are  raised  together. 


on.    n       m  iv      v       vi    v  vr  YIV   m   ir 

Section  from  the  Great  North,  to  the  Little  North,  Mountain,  through  Bore 
Springs,  Virginia,     tf,  positions  of  thermal  spi-in*.'-. 

Fig.  92  represents  an  actual  section  six  miles  long,  from 
a  part  of  the  Appalachians,  illustrating  well  the  flexures. 
But  it  illustrates  another  fact :  that,  since  the  flexures 
were  made,  the  region  has  been  worn  by  waters,  either 
those  of  rivers  or  the  ocean,  so  that  the  tops  of  the  flex- 
ures are  worn  off,  and  where  they  once  were  there  are 
now  often  valleys ;  siich  a  valley  is  represented  in  Fig.  92,  to 
the  left  of  the  middle  above  II.  The  tops  of  such  folds  were 
broken  deeply  while  the  bending  and  stretching  was  in 
progress,  and  the  breaks  would  have  opened  upward;  and 
therefore  these  should  be  the  parts  most  deeply  eroded. 
The  thin  black  layer  over  IV,  on  the  left,  was  once  con- 
tinuous with  IV,  near  the  middle  of  the  section ;  and  so 
with  the  rest.  To  the  right  the  beds  are  vertical. 

Another    view    of    upturned    and    eroded    rocks    as    they 


UFTUIiNINGS   AND   FLEXUllES   OF   HOCKS. 


Ill 


occur  at  a  place  in  western  Colorado  is  given  in  Fig.  93.  The 
strata  in  the  foreground  have  the  dip  and  order  of  superpo- 
sition the  reverse  of  those  more  distant,  showing  that  a  twist 
is  connected  with  the  upturning.  Other  examples  of  folding 

Ym.  93. 


Upturned  Strata  of  the  West  Slope  of  the  Elk  Mountains,   Colorado. 

The  light-shaded  stratum,  Triassieo-.Junis>u-  ;  that  to  the  right  of  it,  Carboniferous;  that 
to  the  left,  Cretaceous. 

and  of  subsequent  degradation,  from  the  Alleghanies,  are  illus- 
trated in  Figs.  94-99.  In  each  case  the  harder  stratum  in  the 
series  determines  in  a  large  degree  the  final  form  of  the  hill 
and  the  landscape  effect  of  the  erosion. 

Fig.  100  represents  a  still   more   remarkable   case   of  flex- 
ures  and   subsequent    erosion ;   the   folded   region  has    been 

Fi«s.  94  —  99. 


Degradation  of  a  Folded  Mountain  Region. 

worn  away  to  a  nearly  level  surface,  so  that  the  existence 
of  flexures  is  to  be  ascertained  only  in  vertical  sections 
of  the  rocks.  Regions  of  such  folded  rocks  are  generally 
very  difficult  to  study,  because  of  the  extensive  erosion. 


112 


MAKING     OF     MOUNTAINS. 


Ledges  and  ridges  in  which  the  strata  slope  only  in 
one  direction  are  often  one  side  or  part  of  a  great  fold. 
But  in  many  cases,  by  slioving  along  faidts  and  over  the 
rocks  beyond  there  is  only  a  slope  in  one  direction  made, 
and  this  is  called  a  monocline)  from  the  Greek  for  one 
and  incline. 


General  View  of  Folds  in  the  Archaean  Rocks  of  Canada. 

'3.  Fractures  and  Faults.  —  Besides  flexures,  great  and 
small  fractures  have  been  made  in  large  numbers  during 
epochs  of  upturning  or  mountain-making.  Fig.  1()1  repre- 
sents strata  thus  broken ;  and,  moreover,  the  beds  are 
faulted  or  displaced  along  the  fractures.  The  beds 
numbered  1,  1,  1  were  once  a  single  continuous  layer; 

FIGS,  lul  —  ln->. 


Fractures  and  Faults. 

and  so  with  the  others;  but  at  the  time  of  fracture  there 
was  a  dropping  of  the  middle  portion,  so  that  along  each 
fracture  there  is  now  a  fault,  or  displacement?.  Another 
ease  is  illustrated  in  Fig.  102;  here  as  the  fracture  was 


UNCONFOBMABLB   STKATA. 


113 


irregular  in  its  course,  the  displacement  has  brought  pro- 
jecting parts  of  the  two  sides  together.  Veins  have  often 
been  rendered  irregular  in  width,  or  entirely  interrupted,  in 
this  way.  Fig.  82  on  page  1)8  is  another  example  of  such 
irregularities.  The  figures  represent  faults  or  displacements 
of  only  a  few  feet  or  yards;  but  in  many  faults,  produced 
in  the  making  of  a  range  of  mountains,  the  rocks  of  one 
side  of  a  fracture  have  been  pushed  up,  or  have  dropped 
down,  thousands  of  feet. 

\Yheii  fractures  are  very  numerous  in  the  rocks  of  a 
region,  and  iu  parallel  planes  of  great  extent  and  regu- 
larity, and  have  the  walls  in  contact  or  nearly  so,  they 
are  called  join  I*. 

4.  Unconformable  Strata.  —  Hocks  are  often  laid  down  hori- 
zontally o/w  n/if i//-/ir<l  rocks ;  the  layers  of  the  two  do  iiot 
then  roiiform  to  one  another.  In  Fig.  103,  rocks  1  and  2  are 

tttf.   10:',. 


Section  from  the  South  Side  of  the  St.  Lawrence,  Canada,  between  Cascade  Point 
and  St.  Louis  Rapids. 

1,  Gneiss  ;  2,  Potsdam  sandstone. 

iiiH'<iiif<i>'in<tble  with  each  other,  while  2  and  those  overlying 
2  are  conformable.  There  is  a  fault  across  the  whole  to 
the  left  of  the  middle;  and  two  others  farther  to  the  left, 
which  are  confined  to  the  lower  beds.  1.  and  which,  therefore, 
were  made  before  the  next  stratum  above.  2,  was  deposited. 


DANA    S     I. KOI..      STOUV ! 


114  MAKING-     OF     MOUNTAINS. 

5.  Earthquakes.  —  The    upturning,    flexing,    and   fracturing 
of   rocks   could   not   have   taken  place   on  so   grand  a  scale 
without   sudden   shakings  or  jars  of  the   rocky   strata;    and 
every  such  jar  was  an  eart/nj>i<ik<j.      A   scratch  of  a   pin    on 
the  end  of  a  log  may  be  heard  by   placing  the  ear  at  the 
other  end,  because  the  vibration  made  by  the  scratch  travels 
along  the  log,  and  with  great  rapidity.     A  jar  in  the  earth's 
crust  or  its  rocks  travels  in  the  same  way.     It  has  often,  in 
modern  times,  been  felt  through  a  large  part  of  a  hemisphere. 
Subterranean  thunder  has  been  a  consequence  of  it;  and  pro- 
found fractures  of  the  earth's  surface,  resulting  sometimes  in 
the  destruction  of  cities  and  human  lives.     Earthquakes  occur 
whenever  there  is  any  yielding  or  slipping  along  a  fracture 
of  the  rocks  beneath  the  earth's  surface;  and  they  are  most 
likely  to   occur   along   the   mountain   border   of   a   continent 
where   have   been   the   greatest    upturnings   and   fracturings. 
They  are  especially  common  where  there  are  volcanoes  along 
such  borders. 

6.  Metamorphism. — The  upturning,  fracturing,  and  flexing 
attending   mountain-making   accounts   for   the    heat  required 
for  metamorphism,  and    for   the    very   wide   extent   of  most 
areas   of  metamorphic   change;    for,  as  has  been  stated,  the 
great    regions    of    metamorphism    are    regions    of    upturned 
rocks. 

7.  Making    of    Material   for    Mountain   Ranges.  —  The   rock 
formations    out   of  which   great    mountain    ranges,   like  the 
Appalachian    range,    have    been    made    include    those    that 


CAUSE    OF     UPLIFTINGS,    FLEXURES,    ETC.  115 

were  deposited  over  the  region  during  many  preceding 
periods.  In  the  ease  of  the  Appalachians,  the  region 
extended  from  near  Albany,  New  York,  to  Alabama  and 
Mississippi,  or  about  900  miles,  and  it  was  over  a  hun- 
dred miles  across  where  widest.  And  the  rocks  that  were 
upturned  are  those  of  all  the  eras  from  the  close  of  the 
Archaean  to  the  close  of  the  Coal  or  Carbonic  era.  As 
most  of  these  rocks  bear  evidence  by  means  of  ripple- 
marks,  and  mud-cracks,  and  in  other  ways,  of  shallow-water 
origin,  it  is  necessarily  inferred  that  the  whole  great  region 
was  undergoing  a  slow  subsidence,  during  the  progress  of 
the  rock-making,  the  depth  of  which  where  greatest  was 
equal  to  the  maximum  thickness  of  the  rocks.  This  great 
syncline  in  the  earth's  crust,  taking  all  Paleozoic  time  to 
make,  and  40.000  feet  deep  in  some  parts,  was  the  prelude 
to  the  making  of  the  Appalachian  range.  A  similar  syncline 
has  preceded  the  birth  of  most  other  mountain  ranges. 

(S.  Cause  of  Upliftings,  Fractures,  and  Flexures,  and  of  Moun- 
tain-Making.—  If  a  quire  of  paper,  lying  on  a  table,  be 
pressed  together  at  the  front  and  back  edges,  it  will  rise  into 
a  fold;  and,  in  case  the  paper  is  of  a  soft  and  inelastic  kind, 
into  a  series  of  folds.  Pushing  from  below  will  make  it  bulge 
upward,  but  only  lateral  pressure  will  make  a  succession  of 
folds.  The  facts  with  regard  to  flexures  in  the  rocks  of 
mountain  regions  prove  that  the  force  which  has  made  the 
great  series  of  folds,  uplifts,  and  fractures  has  acted  lat- 
erally; that  is,  it  was  lateral  pressure  within  the  earth's  crust. 


116  MAK1NC!     OF    MOUNTAINS. 

Mouutaiii  ranges  occur  on  all  the  continents,  showing 
that  the  cause  of  uplift  and  flexure  has  been  a  universal 
one;  and,  in  accordance,  lateral  pressure  within  the  earth's 
crust  is  a  force  necessarily  universal  in  its  action.  Mountain 
ranges  are  hundreds  and  even  thousands  of  miles  in  length; 
and  a  cause  thus  universal  is  sufficient  to  have  made  all, 
whatever  their  length  or  height. 

This  lateral  pressure  is  attributed  .to  the  admitted  fact 
that  the  earth  has  cooled  from  a  state  of  fusion ;  and  that 
the  crust  formed  thickened  below  from  the  continued  cool- 
ing. In  cooling  from  fusion  a  rock  contracts,  losing  on  an 
average  a  twelfth  of  its  bulk ;  and  hence  continued  cooling 
means  continued  contraction,  and  an  effort  to  draw  the 
surface  rock  downward.  The  crust,  under  such  circum- 
stances, would  be  necessarily  put  into  a  state  of  pressure 
of  every  part  against  every  adjoining  part,  like  the  pressure 
between  the  stones  of  an  arch;  and  if  any  part  gave  way, 
or  the  crust  were  flexible  at  all,  there  would  be  uplifts, 
flexures,  breaks,  and  faults. 

The  flexures  in  the  earth's  strata  are,  then,  the  effects  of 
this  lateral  pressure,  and  the  great  mountain  chains  are 
evidence  as  to  its  extent  and  power. 

The  mountain  chains  are  situated,  for  the  most  part,  on 
the  borders  of  the  oceans.  Thus  on  the  Atlantic  border 
there  is  the  Appalachian  chain,  while  on  the  1'anrir  border 
stand  the  lofty  Rocky  Mountains.  Again,  in  South  Aim-i-ica 
there  are  the  Brazilian  Mountains  on  the  east,  and  the  fai' 


CAUSE    OF    CPLIFT1NGS,    FLEXURES,    ETC.  117 

greater  chain  of  the  Ancles  on  the  west.  Other  continents 
illustrate  the  same  truth,  —  that  the  continents  have  high  bor- 
ders and  a  low  interior,  and  also  that  the  highest  border 
faces  the  larger  ocean. 

Moreover,  the  volcanoes  of  the  continents  are,  with  few 
exceptions,  near  the  ocean,  and  far  the  greater  part  of 
them  are  on  the  borders  of  the  Pacific  or  larger  ocean 
(page  W). 

These  facts  prove  that  the  breaks  and  uplifts  that  were 
made  by  lateral  pressure  in  the  earth's  crust  were  mostly 
confined  to  the  borders  of  the  oceans,  and  that  they  were 
most  extensive  on  the  sides  of  the  largest  ocean. 

A  reason  for  this  position  of  the  great  mountain  chains 
near  the  oceans  is  found  in  the  fact  that  the  crust  of  the 
earth  that  lies  beneath  the  ocean's  bed  is  lower  in  level 
than  that  of  the  land,  and  the  basin-like  depression  has 
rather  abrupt  sides  toward  the  continents.  Owing  to  this, 
the  action  of  the  lateral  pressure  from  the  direction  of  the 
ocean  was  obliquely  upward  against  the  land,  and  therefore 
just  what  was  required  to  push  up  the  borders  of  the  conti- 
nents into  mountains,  or  to  produce  flexure  after  flexure  in 
the  yielding  rocks,  or  to  break  them  and  give  outflow  to 
floods  of  lava. 

The  subsidence  during  all  Paleozoic  time,  producing  the 
syncline  or  trough  full  of  strata  out  of  which  the  Appa- 
lachian range  was  made,  has  been  attributed  to  the  weight 
of  fJic  accumulceting  ^tratu  and  not  to  lateral  pressure.  This 


118  MAKING  OF  MOUNTAINS. 

supposed  cause  of  subsidence  is  a  true  cause;  but  whether 
it  was  the  chief  cause  or  not  is  still  undecided. 

9.  Mountain  Chains.  —  Mountain  chains  are  the  result  of 
more  than  one  mountain-making  process.  A  single  example 
will  suffice  to  illustrate  this  truth.  The  whole  area  of  elevated 
land  from  Labrador  to  Alabama  is  called  the  Aj>i>(i/<i<-/,;<i,, 
chain.  But  the  Adirondacks,  the  Highlands  of  New  Jersey, 
and  portions  of  the  Blue  Ridge  of  Pennsylvania  and  Virginia 
were  made  at  the  close  of  Archa-an  time,  long  before  the 
rest.  The  Taconic  Mountains  w.tf  of  the  Adirondacks  were 
next  raised,  being  of  Middle  I'aleo/oic  origin;  then,  after 
other  long  eras  had  passed,  at  the  close  of  Paleozoic  time, 
or  the  Carbonic  era,  the  Appalachian  range  from  Xew  York 
to  Alabama,  west  of  the  line  of  the  Blue  Ridge  and  High- 
lands, was  completed.  Tims  the  Appalachian  rlmin  was  a 
result  of  a  succession  of  mountain-making  efforts,  one  pro- 
ducing one  part,  and  the  rest  others.  The  process  did  not 
go  on  twice  along  just  the  same  line  of  country,  but  to  one 
side  of  the  preceding,  either  east  or  west.  Since  the  com- 
pletion, the  country  has  been  raised  as  a  whole  by  a  gentle 
bending  upward  of  the  earth's  crust,  the  lateral  pressure 
in  this  case,  after  the  mountains  were  made,  and  their  rocks 
folded  and  consolidated,  producing  a  gentle  flexure  of  the 
crust  and  not  any  folding  of  strata. 

In  Mesozoic  time,  after  the  making  of  the  Appalachian 
range,  there  was,  to  the  eastward,  mountain-making  of  a 
different  kind.  Along  the  regions  of  the  Bay  of  Fundy, 


MOUNTAIN    CHAINS.  119 

the  Connecticut  Valley  south  of  New  Hampshire,  and  a  long 
range  of  country  from  the  Palisades  011  the  Hudson  through 
New  .Jersey  and  Pennsylvania  to  and  through  North  Carolina 
(each  region  parallel  to  the  part  of  the  Appalachian  chain 
west  of  it),  where  several  thousand  feet  of  Triassic  sandstone 
had  been  deposited,  there  occurred,  finally,  together  with 
a  small  upturning  of  the  strata,  a  great  fracturing  of  the 
earth's  crust,  the  fractures  deep  enough  to  let  out  melted 
rock;  and  this  rock,  cooled,  constitutes  the  Palisades  on  the 
Hudson,  Mount  Holyoke  in  Massachusetts,  East  and  West 
Rock  near  New  Haven  in  Connecticut,  and  various  other 
trap  ridges  in  the  Connecticut  Valley,  Nova  Scotia,  and  the 
more  southern  sandstone  regions.  Here  the  lateral  pressure 
produced  little  upturning,  but  much  fracturing,  with  exten- 
sive igneous  ejections;  and  this  exemplifies  a  second  method 
of  action  in  mountain-making,  a  method  which  was  most 
common  in  the  later  part  of  geological  time.  After  this 
epoch  of  disturbance  there  was  no  other  general  upturning 
along  this  Atlantic  border.  Mountain-making  was  there  for 
the  most  part  ended.  But  on  the  Pacific  side,  the  Kocky 
Mountains  were  not  finished  before  the  close  of  the  Creta- 
ceous period,  when  the  long  Laramide  mountain  system, 
reaching  from  near  the  Arctic  Sea  to  Central  America,  was 
made.  Moreover,  the  area  of  the  Rocky  Mountains  was  not 
lifted  to  its  present  height  before  the  close  of  the  Tertiary. 
In  like  manner,  the  last  mountain-making  in  the  chain 
of  the  Alps  and  Himalayas  was  delayed  until  the  close  of 


120  MAKING    OF    MOUNTAINS. 

the  Middle  Tertiary;  and  after  that  time  the  Alps  received 
10,000  feet  of  their  height  and  the  Himalayas  20,000  feet. 
Moreover,  to  this  later  part  of  geological  time,  the  Cretaceous 
and  Tertiary,  belong  the  greatest  of  all  volcanoes  and  igneous 
eruptions  over  the  world. 

10.  Making    of    Continents   and    the   Oceanic    Depression.  — 
Contraction  from  cooling  also  gives  a  reason  for  the  exist- 
ence of  the  great  depressions  occupied   by  the  oceans;  for, 
on  this  view,  they  are   the   parts   of   the  earth's  crust  that 
have    sunk    most    with    the    progressing    contraction,  —  the 
parts,  therefore,  which   were   last   stiffened,  when   the    crust 
was  in  process  of  formation;   while  the  continents  were  the 
portion  that  contracted  least,  or  which  first  became  solid. 

11.  Conclusion.  —  There    is    thus,  in   the   single   fact   that 
the  earth  is,  and  ever  has  been,  a  cooling  globe,  and  there- 
fore  universally   a  contracting   globe,  an   explanation  (1)  of 
the   gentle   oscillations   of   level  in   the  earth's  surface,  that 
have   been   quietly   going   on   through  all  past  time ;    (2)  of 
the  upturnings,  flexures,  fractures,  faults,  and   upliftings  of 
strata,   and   the   bendings   of  the   earth's   crust,  which  have 
resulted    in    the   making   of    the    great  mountain   chains   of 
the  globe;  (3)  of  the  opening  of  fractures  down  to  the  deep- 
seated  regions   of  fire   giving   exit  to  floods   of   liquid   rock 
and  producing  volcanoes;   (4)  of  the   alteration   of  rocks,  or 
their   metamorphism,  changing  the  rude  sand-beds  and  mud- 
beds   into   crystalline   rocks,   and  filling  fissures   with  veins 
of  ores  and  gems;  (5)  of  earthquakes,  the  great  earthquakes 


CONCLUSION.  121 

and  the  larger  part  of  the  smaller  ones;  and,  finally,  (6)  an 
explanation  of  the  origin  of  continents. 

It  may  be  thought  that  by  thus  referring  to  secondary 
causes  the  making  and  crystallizing  of  rocks,  the  placing 
and  raising  of  mountain  chains,  and  even  the  defining  of 
continents,  we  leave  little  for  the  Deity  to  do.  On  the 
contrary,  we  leave  all  to  him.  There  is  no  secondary  cause 
in  action  which  is  not  by  his  appointment  and  for  his  purpose, 
no  power  in  the  material  universe  but  his  will.  Man's  body 
is,  for  each  of  us,  a  growth;  but  God's  Avill  and  wisdom 
are  manifested  in  all  its  development.  The  world  has  by 
gradual  steps  reached  its  present  perfected  state,  suited  in 
every  respect  to  man's  needs  and  happiness,  —  as  much  so 
as  his  body;  and  it  shows  throughout  the  same  Divine  pur- 
pose, guiding  all  things  toward  the  one  chief  end,  —  man's 
material  and  spiritual  good. 


PART    III. 

HISTORICAL   GEOLOGY. 
SUBJECTS   AND    SUBDIVISIONS. 

HISTORICAL  GEOLOGY  treats  of  :  — 

1.  The   succession   in   the   formation  of  the  rocks  of  the 
earth,  and  in  the  conditions  under  which  they  were  made. 

2.  The    progress    in    the    continents,    from     their     small 
beginnings   to  their   present   magnitude. 

3.  The   changes  of  level  ever   going   on,  and    the   raising 
of    mountain    ranges    at    long    intervals,    the    highest    and 
longest   in   the   later    part  of    geological    time,   just    before 
the   era   of  Man. 

4.  The  multiplication  of  rivers  as  the  dry  land  extended, 
and  thereby  the  excavation  of  valleys,  the  shaping  of  lofty 
ridges  giving  grandeur  to  the  mountains,  and  the  spreading 
of   the   lower   lands   with   soil   and   fertility. 

5.  The  changes  in  climate,  from  the  universal  warmth  of 
the  Archaean  world  to  the  existing  variety  of  heat  and  cold. 

6.  The   succession   in   the  .species    under   the    two    king- 

m 


CRITERION   OF    AGE   OF   STRATA.  123 

doms  of  life.  Plants  anil  Animals,  from  the  simpler  forms 
of  early  time  to  Man. 

The  rocks  are  sometimes  spoken  of  as  the  leaves  of  the 
geological  record.  But  these  rocks  are  in  various  lands, 
here  some  and  there  others;  and  how  can  they  be  brought 
into  order  so  as  to  make  a  continuous  history  worthy  of 
confidence  ?  The  case  would  have  been  hopeless  were  it 
not  for  one  branch  of  this  history,  —  that  relating  to  the 
2>royre#is  of  life.  There  has  been,  as  above  intimated,  a 
succession  in  the  species  of  plants  and  animals  that  have 
lived  upon  the  globe.  Tin-  curliest  kinds  were  followed  by 
others,  and  these  by  still  others,  and  so  on,  through  age 
after  age,  before  the  final  appearance  of  Man.  The  plants 
and  animals  that  lived  in  the  successive  periods  left  their 
relics  —  that  is,  stems  or  leaves,  shells,  corals,  bones,  and 
the  like  —  in  the  mud  or  sand  of  the  sea-bottom,  seashore 
flats,  and  beaches,  and  in  other  deposits  of  the  era;  and 
these  sand-beds  and  mud-beds  are  now  the  rooks  of  those 
periods.  Hence  in  the  rocks  of  one  era  AVC  find  different 
relics,  or  fossils,  from  those  of  the  preceding  or  following 
era.  Geologists  have  ascertained  the  kinds  that  belong  to 
the  successive  rocks,  or  eras  of  the  world;  so  that,  if  they 
come  upon  an  unknown  rock  with  fossils,  in  a  country 
not  before  studied,  it  is  only  necessary  to  compare  the 
fossils  found  with  the  lists  already  made  out. 

For  a  long  part  of  early  time  after  life  was  abundant 
there  were  no  fishes  in  the  world.  The  discovery  of  a 


124  HISTORICAL   GEOLOGY. 

fossil  fish  in  a  bed  of  rock  is  evidence  that  the  bed 
does  not  belong  to  the  formations  of  that  earliest  time, 
but  to  one  of  some  later  period.  After  the  first  appear- 
ance of  fishes  the  kinds  changed  with  the  progress  of  time; 
so  that  if,  in  the  case  of  our  discovery,  we  can  ascertain 
the  subdivision  of  the  class  to  which  our  fossil  fish  be- 
longed, we  can  then  decide  approximately  the  age  of  the 
rock  which  afforded  it.  No  herring,  cod,  and  salmon  are 
known  to  have  existed  until  near  the  last  of  the  geolog- 
ical ages;  and  if  the  species  turned  out  to  be  related  to 
these,  we  should  conclude  that  the  rock  was  among  the 
later  in  geological  history ;  and  a  determination  of  the 
species  might  lead  to  the  precise  epoch  to  which  it  per- 
tained. Bones  of  beasts  of  prey,  cattle,  and  horses  are 
found  only  in  rocks  of  the  last  two  geological  eras. 

Thus,  owing  to  the  succession  of  life  on  the  globe,  the 
geologist  is  enabled  to  arrange  the  fossiliferous  rocks  in 
the  order  of  their  formation,  —  that  is,  the  order  of  time. 

If  a  stratum  in  one  locality  contains  110  fossils,  or  if  its 
fossils  have  been  obliterated  by  heat  producing  metamor- 
phism,  the  stratum  is  traced  by  the  geologist  to  another 
locality,  with  the  hope  of  there  discovering  fossils,  or  at 
least  of  finding  them  in  an  underlying  or  overlying  stratum. 
In  this  and  other  ways  doubts  are  gradually  removed,  and 
the  true  succession  in  any  region  is  made  out. 

The  history  has  thereby  been  divided  into  four  grand 
sections :  — 


CLASSIFICATION   OF   ANIMALS.  125 

I.  ARCH^EAX   TIMK;    that   is,    Iwyiuniny  time;    the   word 
Archaean  is   from   the   Greek   for    beginning. 

II.  PALEOZOIC    TIME,  or  the   era  of  the  ancient  forms  of 
life;    Paleozoic   being   from   the   Greek   for   ancient   and  life. 

III.  MESOZOIC    TIME,   or   the   era   of    mediceval   forms   of 
life ;    Mesozoic,   from   the   Greek,  signifying   middle  and  life. 

IV.  CEXOZOK:   TIME,  or  the   era  of  the  more  recent  forms 
of   life ;    Cenozoic   signifying    recent   and   life. 

Paleozoic,  time,  which  was  probably  threefold  longer  than  all 
later  time,  has  been  divided  into  five  eras:  (1)  the  CAMBRIAN; 
(2)  the  LOWER  Sn.ruiAx;  (8)  the  UPPER  SILURIAN;  (4)  the 
I  )K v<  »\  i  A x ;  and  (/>)  the  C AKBOXK;  ERA.  The  Cambrian  and  the 
Lower  Silurian  eras  correspond  to  the  REIGX  OF  TRILOBITES, 
the  Upper  Silurian  and  Devonian  to  the  EEIGX  OF  FISHES,  and 
the  Carbonic,  era  to  the  REIGX  OF  AMPHIBIAXS. 

Mesozoic   time    corresponds   to   the    REIGX   OF    REPTILES. 

Cenozoic  time  is  divided  into  two  eras,  called  (1)  the 
TERTIARY,  or  ERA  OF  MAMMALS;  and  (2)  the  QUATER- 
XARY,  or  ERA  OF  MAN. 

The  above-mentioned  names  of  the  grander  divisions  of 
geological  time  give  a  general  idea  of  the  progress  in  life. 
For  its  better  appreciation  a  brief  account  is  here  given  of 
the  principal  groups  in  the,  classification  of  animals. 

Classification  of  the  Animal  Kingdom. 

The  kingdom  of  Animals  has  five  primary  divisions  —  Pro- 
tozoans, Radiates,  Non-articnlates,  Articulates,  and  Vertebrates. 


126  HISTORICAL    (JEOLOGY. 

1.  Protozoans. — These  are  mostly  microscopic  species,  with 
no   differentiation   into   tissues   and   organs.     Most   of   them 
have   not    even   a   mouth.      In   the   typical    Protozoans,   the 
body  consists  only  of  a  single  cell.     The  Rhizopods  (p.  48) 
and    lladiolarians    (p.    oo)    are    here    included.      The    word 
Protozoan,  from   the   Greek,  means  frrxt   or  .s///jy;/<>.s/    <miii«il. 
Sponges  are  of  a  little  higher  grade.     They  are  large,  con- 
sisting of  numerous  cells,  but  the  cells  show  little  differen- 
tiation. 

2.  Radiates.  —  Animals    having  a   radiated  structure ;    that 

Fi<;.  104. 


Astraea  pallida  D. 

is,  having  the  parts  arranged  radiately  around  a  center. 
In  most  of  the  species,  the  mouth  is  situated  at  or  near  the 
center,  as  in  polyps,  the  animals  of  Corals,  which  look  very 
much  like  flowers  on  account  of  the  radiate  arrangement. 
Each  one  of  the  expanded  polyps  in  a  living  Coral  (Fig. 


CLASSIFICATION    OF    ANIMALS. 


127 


10J)  shows  well  the  ratlin/i-  character.  For  other  figures 
see  pages  44,  45,  and  4(>. 

The  Crinouls,  represented  on  page  47,  are  other  exam- 
ples of  Radiate  animals. 

o.  No n- Articulates.  —  1.  J/o//»*>ro/V/.s.  —  Molluscoids  are  di- 
vided into  Bracliiopods  and  Bryozoans. 

A  Bmchiopod  has  a  pair  of  shells,  or  in  other  words, 
a  shell  consisting  of  two  valves  like  a  Clam,  Scallop,  or 
Oyster.  But,  as  Figs.  lOo  to  112  show,  the  shells  are  sym- 

FK;S.   KI.V112. 

-^.<  no 


Brachiopods. 

Fig.  105,  Waldheirala  flavescens  ;  106,  loop  of  Terebratula  vitiva  ;  10",  Terebratulina  cai>ut- 
serpentls ;  109,  Spirifer  sti-iatus  ;  109,  same,  showing  interior  of  dorsal  valve  ;  110,  Athyris 
coucentrica ;  111,  Atrypa  retleularis  ;  112,  same,  showing  interior  of  dorsal  valve. 

metrical  in  form,  so  that  a  vertical  line  through  the  middle 
(Fig.  110)  divides  them  into  equal  halves.  Moreover,  the 
valves  are,  respectively,  dorsal  and  ventral,  not,  as  in  the 
Clam,  right  and  left. 

Inside   of  the  shell  there  is  often  a  loop-shaped  or  spiral 


128 


HISTORICAL    GEOLOGY. 


Rhynchonella  psitta- 
cea,  showing  the 
spiral  arms. 


arrangement  for  the  support  of  a  pair  of  spiral  arms.     In  Fig. 
113  one  of  these  arms  is  rolled  up  spirally,  and  the  other  is 
FIG.  us.  extended  out  of  the  shell.     The  mouth  is 

opposite  the  middle  of  the  lower  margin, 
whereas  in  a  Clam  it  is  at  one  end. 

Bryozoans  are  minute  species,  but  they 
form  compound  groups,  many  of  which  re- 
semble Corals  in  form  and  stony  texture. 
The  animals  look  like  polyps  externally,  as 
shown  in  Fig.  114,  which  represents  them 
projecting  out  of  their  cells,  enlarged  to 
eight  times  their  natural  size.  Fig.  114  a  shows  the  animal 
wholly  out  of  its  cell  and  more  enlarged.  Fig.  115  is  a 
a  view  of  one  of  the  delicate  Cor-  FH;S.  114,  nr>. 

als,  natural  size;  the  dots  show 
the  positions  of  the  little  cells 
of  the  animal.  The  species  are 
called  Bryozoans,  meaning  moss- 
animals,  the  name  alluding  to 
the  Corals,  which  are  sometimes 
moss-like  in  delicacy  and  form. 
They  also  make  crusts  over  shells 
and  stones.  Although  so  small,  these  Bryozoaii  Corals  arc 
a  prominent  constituent  of  some  ancient  limestones. 

2.  Mollusks.  —  These  are  animals  l:.ke  the  Oyster,  Clam, 
Snail,  and  Cuttlefish;  having  a  soft,  fleshy,  bag-like  body, 
with  sometimes  an  external  shell  for  its  protection,  or  an  inter- 


114 


Bryozoans. 

Fig.  114,  Kseliara,  showing-  animals 
extended  out  of  their  cells  ( x  s>; 
1 14  «,  one  of  the  animals  remo\  rl| 
from  its  cell  more  enlarged  ;  115, 
Ptilodictya  feiiestrata,  natural 
si/e  ;  llau,  portion  of  surface  of 
wiine  enlarged. 


CLASSIFICATION   OF   ANIMALS. 


129 


nal  bone  or  shell  to  give  a  degree  of  firmness  to  the  fleshy  body. 
The  following  are  the  principal  groups  :  — 

Lainellibranchs  have  bivalve  shells  as  in  the  Clam,  Mussel, 


FIG.  119. 


117 


FIGS.  116-118. 


116 


Mollusks. 

Fig.  116,  LAMELLIBEANCH  :  Avicula  Trentonensis ; 
Figs.  117, 118,  GASTROPODS  :  117,  Murchisonia 
bicincta ;  118,  Pleurotomaria  lenticularis. 

and  Oyster.     Fig.  116  shows  one  of  the 
Mussel-like    species.     They   are   called 
Lainellibranchs    because    the    gills    (or 
branchiae),  which  lie  against  the  body 
on  either  side,  are  thin,  lamellar  organs. 
Gastropods    include    Snails    and    all 
i  other  species  having  a  spiral  shell  and 
a  single  continuous  chamber  within,  and 
also  some  species  with  shells  of  other 
forms,  and  some  without  shells.     Figs. 
117,  118  are   examples.     The   name  is   from   the   Greek  for 
venter,  or  the   under  side  of  the  body,  and  foot,  because  the 
animals  crawl  on  the  ventral  surface. 
DANA'S  GEOL.  STORY  —  9 


Modern    Pteropod. 
Styliola  (x  o£). 


130 


HISTORICAL   GEOLOGY. 


Pteropods,  now  represented  only  by  a  few  small  species, 
having  thin  translucent  shells  (or  none),  have  often  slender 
conical  forms,  and  this  was  the  common  form  in  ancient  time. 
As  Fig.  119  shows,  they  are  furnished  with  short  paddles, 
which  they  put  out  for  use  in  swimming.  The  figure  repre- 
sents a  species  from  the  Gulf  of  Mexico,  five  and  a  half 
times  its  natural  size. 

Cephalojwds,  the  highest  of  Mollusks,  are  so  named  from 
the  Greek  for  head  and  foot,  the  feet  or  arms  being  arranged 

FIG.  120. 


Modern  Cephalopod. 

The  Calamary  or  Squid,  Loligo  vulgaris  (length  of  body,  6  to  12  inches) ;  i,  the  funnel 
through  which  the  water  and  ink  are  thrown  out;  p,  the  "pen." 


around  the  mouth.  The  eyes  are  very  large  as  in  Fishes. 
In  one  division  of  them,  that  of  the  Squids  and  related  species 
(Fig.  120),  the  animal  has  an  internal  bone  (p)  sometimes 
called  from  its  form  the  pen,  and  no  external  shell.  The 
body  is  inclosed  in  a  bag  or  outer  tunic,  which  is  open  a 
little  distance  back  of  the  eyes,  and  the  animal  propels 
itself  backward  through  the  water  by  taking  in  and  ejecting 
water  from  the  bag.  It  has  an  ink-bag  inside,  to  enable  it 


CLASSIFICATION   OF    ANIMALS.  131 

to  becloud  the  water  when  pursued.  The  funnel,  through 
which  the  Avater  and  ink  are  thrown  out,  is  shown  at  ?', 
Fig.  120. 

The  Nautilus  (Fig.  121)  is  an  example  of  a  Cephalopod 
having  a  coiled  external  shell.  FIG.  121. 

The  figure  presents  a  vertical 
section  of  the  shell,  and  shows 
that  it  is  divided  by  transverse 
partitions  into  a  series  of  cham- 
bers. The  animal  occupies  the 
outer  chamber,  but  has  organic 

connection    with    the    interior  Modem  Cephalopod. 

through    a    membranous    tube  Nautilus  (x  j). 

called  a  siphuncle.  In  these  chambers,  the  shells  differ  from 
those  of  Gastropods. 

4.  Articulates.  — These  include  Worms  and  Crustaceans,  the 
water  species,  and  Myriapods,  Spiders,  and  Insects,  the  land 
species.     They  are  distinguished  by  having  the  body  and  its 
members  made  up  of  joints  or  segments,   articulate  meaning 
jointed. 

Crustaceans  include  Crabs,  Lobsters,  Shrimps,  and  other  spe- 
cies ;  and  are  so  named  because  they  have  a  crust-like  exterior 
which  is  sometimes  called  the  shell. 

5.  Vertebrates.  —  The  higher  and  more  typical  Vertebrates 
have   internally,   along  the   back,   a  series  of  bones  making 
together  the  vertebral  column.     In  Fig.  122,  representing  one 
of  the  gigantic  Mammals  of  ancient  time,  the  vertebral  column 


132 


HISTORICAL   GEOLOGY. 


is  seen  extending  from  the  head  into  the  tail.  Each  separate 
bone  of  the  column  is  called  (from  the  Latin)  a  vertebra.  The 
great  nerve  of  the  body,  called  the  spinal  cord,  lies  concealed 
in  a  tubular  bone-sheathed  cavity  along  the  dorsal  side  of  the 
column ;  and  on  the  ventral  side  of  the  column  there  are  the 
ribs  and  the  cavity  for  the  stomach  and  other  viscera.  Some 
of  the  lower  Vertebrates  exhibit  the  characteristic  vertebral 
skeleton  only  in  a  rudimentary  state  of  development. 

Fro.  122. 


Vertebrate . 
Tinoceras  Ingens. 

The  principal  subdivisions  of  Vertebrates  are  Fishes, 
Amphibians,  Keptiles,  Birds,  and  Mammals. 

1.  Fishes.  —  The  species  breathe  by  gills.  They  have  gen- 
erally two  pairs  of  fins  on  the  under  surface,  the  pectoral  and 
the  ventral,  corresponding  to  the  two  pairs  of  limbs  of  higher 
Vertebrates. 


CLASSIFICATION    OF    ANIMALS.  133 

2.  Amphibians,  or  Frogs  and  Soiamanden.  —  Amphibians 
have  gills  in  the  young  or  tadpole  state,  and  lose  the  same  on 
becoming  adult.     In  the  change  from  the  tadpole,  or  fish-like 
stage,  to  that  of  the  Frog,  there  is  a  loss  also  of  the  tail ;  but 
the  Salamander  retains  the  tail  through  life  and  thus  has  the 
form  of  a  Lizard.     All  other  Vertebrates  breathe  only  by  lungs. 

3.  Reptiles.  —  Eeptiles  have  the  body  either  naked  or  covered 
by  scales  or  bony  plates,  and  are  oviparous. 

4.  Birds.  —  Birds   are   covered   by   feathers    and   are   also 
oviparous. 

5.  3fa  initials. —  Mammals  suckle  their  young,  as  the  word 
from  the  Latin  implies.     They  are  the  highest  of  Vertebrates, 
and  include  Man  as  well 'as  the  Dog,  Cat,  Horse,  Seal,  and 
Whale. 

All  animals  that  are  not  Vertebrates  are  called  Invertebrat.es. 

In  the  Cambrian  era  and  part  of  the  Lower  Silurian,  the 
animals  were  all  Invertebrates. 

In  the  table  on  page  125  the  expressions  Reign  of  Trilobites, 
Reign  of  Fishes,  Reign  of  Reptiles,  Reign  of  Mammals,  etc.,  are 
not  to  be  understood  as  implying  that  the  several  groups  of 
animals  mentioned  were  confined  to  the  era  named  in  connec- 
tion with  them,  but  only  that  they  were  the  most  character- 
istic species  of  the  era. 

Fishes  began  before  the  Lower  Silurian  era  was  completed, 
and  continued  on  through  geological  time ;  but  until  the  close 
of  the  Devonian  they  were  the  highest  of  living  species. 

Under  the  Eeign  of  Reptiles,  the  class  of  Reptiles,  which 


134  HISTORICAL   GEOLOGY. 

began  in  the  preceding  era,  had  larger,  more  numerous,  and 
higher  species  than  before  or  afterward ;  the  era  was  emi- 
nently that  of  the  Reign  of  Reptiles,  the  type  having  reached 
its  maximum  then ;  that  is,  having  culminated. 

Mammals  of  a  low  order  called  Marsupials  existed  in  the 
Mesozoic,  or  during  the  Reign  of  Reptiles  ;  but  during  the 
Cenozoic,  or  the  Reign  of  Mammals,  Reptiles  were  compara- 
tively few,  and  ordinary  Mammals  were  the  highest  and  the 
dominant  race.  Again,  the  era  of  Coal-plants  was  not  the  only 
era  in  which  coal-plants  lived  and  coal  was  made ;  but  it  was 
the  era  which  was  most  remarkable  for  the  making  of  coal-beds, 
and  especially  for  coal-making  plants  of  the  tribe  of  Acrogens, 
the  highest  of  Cryptogams,  such  as  Ferns,  Ground  Pines  or 
Lycopods,  and  Horsetails  or  Equiseta,  which  then  grew  to  the 
size  of  tall  shrubbery  and  forest  trees.  In  later  ages  also  coal- 
beds  were  made,  but  of  less  extent,  and  mainly  out  of  other 
kinds  of  plants.  The  Carbonic  era  is  often  called  the  Era 
of  Acrogens,  and  also  the  Era  of  Amphibians. 

During  the  progress  of  an  era,  changes  of  level,  or  catas- 
trophes of  some  other  kind,  have  at  intervals  produced  exten- 
sive disappearances  of  species  over  a  Continental  sea,  and  also 
abrupt  changes  in  the  kinds  of  rock-deposits  in  progress,  if  not 
also  upturnings  of  strata.  Such  events  are  made  the  bases  of 
subdivision  of  eras  into  periods  and  epochs. 

The  following  table  gives  a  general  view  of  the  successive 
eras,  with  some  of  the  subdivisions  that  have  been  adopted ; 
the  first  in  time  or  earliest  being  at  the  bottom. 


TABLE   OF   GEOLOGICAL    ERAS. 


135 


Eras. 


Subdivisions. 


[  2.  Quaternary  

AMERICAN. 

{3.  Recent. 
2.  Champlain.  ] 

BRITISH. 
Kecent. 

CENOZOIC.. 

j 
1.  Tertiary  

1.  Glacial.        J 
("3.  Pliocene. 

Pleistocene. 
Pliocene. 

MESOZOIC. 

.  .  .  Reptilian  

[  1.  Eocene. 
f  8.  Cretaceous. 

Miocene. 
Eocene. 

Cretaceous. 
(Jurassic  including 
2    Oolvte 

[  1.  Triassic. 

1.  Lias. 
Triassic. 

PALEOZOIC. 


f«. 

Permian.                          Permian. 

r  3  Carbonic  .  . 

J  2 

Carboniferous                  Carboniferous 

I? 

Subcarboniferous.           Mountain  limestone. 

Portage  and  Chemung.  ~\ 

i- 

2.  Devonian  .  .  . 

{J 

r 

Hamilton. 
Corniferous.                    -  Old  red  sandstone. 

u. 

Oriskany.                        J 

1.  U.  Silurian.. 

ft, 

a 

Lower  Helderberg.        Ludlow  group. 

Onondaga.  1 
„.                  >                   Wenlock  group. 
Niagara. 

. 

'  2.  L.  Silurian  .  . 

it 

Trenton.               Llandeilo  and  Bala  groups. 
Canadian.             Arenig  group. 

jj  - 

ra. 

Later.      1 

1  .  Cambrian  .   . 

.2. 

Middle.    L            Cambrian. 

i  * 

Early. 

ARCH^AN. 


The  map  on  page  136  (Fig.  123)  shows  the  positions 
of  the  rocks  of  the  successive  ages  that  are  exposed  to  view 
over  the  eastern  part  of  the  continent  of  North  America.  The 
markings  indicating  the  age  of  the  rocks  of  the  several  areas 
are  explained  on  the  map.  The  black  areas  are  the  great 
coal  areas  of  the  continent.  The  portions  left  in  white  are 
areas  of  crystalline  rocks  which  are  partly  Archaean  and 
partly  Lower  Silurian. 


FIG.  123. 


ARCHAEAN   TIME.  137 

I.    ARCHAEAN   TIME. 

The  first  condition  of  the  earth  about  which  geology  gives 
us  any  hint  is  that  of  a  liquid  globe,  or  a  globe  liquid  at 
least  at  the  surface,  for  mere  pressure,  it  is  now  believed, 
would  have  made  the  interior  solid.  Evidence  is  found  in 
the  crystalline  character  of  the  oldest  rocks;  in  the  fact 
that  many  spheres  in  space,  like  the  sun,  are  still  in  such 
a  state  ;  and  in  the  condition  of  the  moon,  which  is  like  a 
globe  that  has  cooled  until  its  surface  is  all  craters  and  scoria. 

Admitting  that  the  earth  has  cooled  from  fusion,  we  are 
warranted  in  concluding  that,  whenever  the  vapors  about 
the  globe  began  to  settle  over  the  solidified  but  still  hot 
crust,  there  to  make  oceans,  the  rocks  exposed  to  the 
heated  and  acid  waters  would  have  been  eroded  by  the 
chemical  action  of  those  waters,  and  by  this  means  they 
would  have  been  covered  after  a  while  with  new  rock 
deposits.  Moreover,  wherever  rocks  were  within  reach  of 
the  waves,  whether  emerged  or  submerged,  the  waves  would 
have  aided  in  making  gravel,  sand,  and  mud,  and  would 
have  distributed  the  detritus  in  beds  and  strata. 

By  such  means  the  original  rock  of  the  cooled  crust  would 
have  become  nearly  or  entirely  concealed  by  new  rock  for- 
mations. It  is  questioned  whether  any  part  of  the  original 
cooled  surface  is  now  exposed  to  view.  The  rocks  made 
out  of  that  crust,  and  not  those  of  the  original  crust  itself, 
are  therefore  the  Archaean  rocks  of  geology. 


138  ARCHAEAN    TIME. 

E.OCKS. 

The  Archsean  rocks  of  North  America  cover  a  large  sur- 
face over  the  northern  portion  of  the  continent,  and  also 
some  narrow  areas  elsewhere  along  the  courses  of  existing 
mountains.  In  the  map  on  page  139  (Fig.  124)  the  white 
areas  are  the  regions  of  exposed  Archaean  rocks.  The 
largest  of  them  extends  from  Lake  Superior  northwest  to 
the  Arctic  seas  and  northeast  to  Labrador.  It  has  rudely 
the  shape  of  the  letter  V,  and  Hudson  Bay  is  included 
within  the  arms  of  the  V.  A  peninsula  stretching  down 
from  it  into  northern  New  York  is  the  region  of  the 
Adiroudacks.  An  interrupted  series  of  Archaean  areas 
extends  along  the  Green  Mountains,  the  Highlands  of  New 
Jersey,  the  Blue  Ridge  of  Pennsylvania  and  Virginia,  the  Black 
Mountains  of  North  Carolina,  and  the  region  farther  southwest. 
Another  such  series  commences  in  Newfoundland  and  extends 
along  Nova  Scotia,  New  Brunswick,  and  near  the  coast  of 
Maine.  The  map  gives  the  positions  of  other  areas  to  the 
west,  the  longest  of  which  is  that  of  the  summit  of  the 
Rocky  Mountains,  including  the  Front  or  Eastern  Range 
in  Colorado,  and  extending  north  into  British  America. 

The  arms  of  the  great  V,  or  original  nucleus  of  the  conti- 
nent, are  approximately  parallel  respectively  to  the  Atlantic 
and  Pacific  coast  lines ;  the  other  narrower  areas  follow  the 
courses  of  the  great  mountain  chains,  and  are  parallel  to 
the  same  lines.  Geology  thus  affords  proof  that  even  in 


ROCKS. 


139 


Archaean  time  the  great  outlines  of  the  continent  were 
denned,  and  that  all  future  progress  was  carried  forward 
by  working  on  the  plan  thus  early  laid  down.  The  rest 
of  the  continent  was  under  water  (and  perhaps  also  some 

FIG.  124. 


Archaean  Map  of  North  America.    White  Portions  Archeean  Rocks. 

of  the  ridges  just  referred  to),  but  the   rocks   probably  lay 
at  no  great  depth. 

Archaean  areas  exist  also  in  Scandinavia,  Bohemia,  Scotland, 
and  some  other  regions.  The  facts  prove  that  in  Archaean 
time  the  ocean  and  continents  were,  in  the  main,  already 


140  ARCHAEAN    TIME. 

outlined.  "The  waters"  of  the  world  had  been  "gathered 
into  one  place,"  and  "the  dry  land"  had  "appeared." 

The  Archaean  rocks  comprise  gneiss  and  granite;  syenyte, 
syenitic  gneiss,  and  other  hornblendic  rocks;  chlorite  schist, 
mica  schist,  quartzyte,  limestone,  and  other  kinds. 

They  include  immense  beds  of  iron  ore,  some  of  them  100 
to  200  feet  in  thickness,  vastly  exceeding  any  of  later 
time;  for  the  Archaean  was  the  Iron  age  in  the  earth's 
history.  These  beds  of  ore  occur  in  northern  New  York, 
Canada,  southern  New  York,  northern  New  Jersey,  North 
Carolina;  in  the  Marquette  region  south  of  Lake  Superior; 
in  Missouri,  where  there  are  what  are  called  Iron  Moun- 
tains ;  and  in  many  other  places.  The 

FIG.  125. 

beds  of  ore  (i,  Fig.  125)  lie  between 
beds  of  quartzyte,  gneiss,  hornblendic 
gneiss,  and  other  rocks  of  the  era, 

Beds  of  iron  Ore  (i),  Essex     as  illustrated   in   the  annexed  cut  rep- 
County,  New  York. 

resenting   a   section    in   Essex   County, 

New  York.  Hornblende  contains  much  iron,  and  is  a  com- 
mon constituent  of  Archaean  rocks. 

The  rocks  were  for  the  most  part  originally  sedimentary 
deposits ;  for  the  gneiss  and  other  schists,  and  also  the  quartz- 
yte, are,  as  explained  011  page  94,  altered  or  metamorphic  sedi- 
mentary rocks ;  they  were  originally  deposits  of  gravel,  sand, 
and  mud  made  by  the  ocean.  The  stratification  in  the  gneiss 
and  other  rocks  is  in  general  the  original  stratification  of 
the  fraginental  beds.  The  quartzyte  differs  but  little  except 


ROCKS. 


141 


in  hardness  from  much  sandstone.  In  Wisconsin  some  of 
the  beds  associated  with  the  iron  ores  are  scarcely  at  all 
crystalline,  the  metamorphic  change  having  been  slight. 

Like  other  sedimentary  deposits,  the  rocks  were  laid 
down  in  horizontal  beds.  But  they  are  now  upturned  at 
all  angles,  and  often  folded,  showing  thereby  that,  subse- 
quently to  their  deposition,  they  underwent  the  great  dis- 
turbances that  attend  mountain-making.  Fig.  126  shows  the 
general  condition  of  the  rocks  in  the  Archaean  regions  of 


FIG.  126. 


General  View  of  Folds  in  the  Archaean  Rocks  of  Canada. 

Canada.  The  Archaean  mountains,  including  the  Adiron- 
dacks,  the  New  Jersey  Highlands,  the  mountains  of  Scandi- 
navia, and  others,  were  made  at  the  close  of  Archaean  time, 
if  not  in  part  earlier.  The  original  height  of  these  moun- 
tains may  have  been  many  thousands  of  feet  greater  than 
it  is  now,  for  all  the  earth's  agencies  of  destruction  have 
been  engaged  in  the  work  of  leveling  them  ever  since  that 
first  of  the  geological  ages. 

Many  Archaean  crystalline  rocks  much  resemble  the  crys- 
talline rocks  of  later  time,  and  as  both  are  without  fossils 
they  may  be  easily  confounded. 

The  occurrence  of  beds  of  iron  ore  scores  of  feet  thick 
is  one  means  of  distinguishing  areas  of  Archaean  age. 


142 


AKCH^EAN   TIME. 


Coarse  syenitic  rocks  and  labradorite  rocks  are  character- 
istic of  many  Archaean  regions,  although  not  exclusively 
Archaean. 

Sure  evidence  of  Archaean  age  is  obtained  when  fossilifer- 
ous  beds  of  the  lowest  Paleozoic  formations  are  observed 
overlying  unconformably  upturned  crystalline  rocks,  as  in 
Fig.  127.  Here  the  nearly  horizontal  Cambrian  beds  No.  2, 

FIG.  127. 


Section  from  South  Side  of  the  St.  Lawrence,  Canada,  between  Cascade  Point  and 
St.  Louis  Rapids. 

1,  Gneiss ;  2,  Cambrian  sandstone. 


with  those  above,  were  laid  down  after  the  beds  below 
were  made,  and  also  after  their  upturning;  and  conse- 
quently the  evidence  that  the  latter  belong  to  anterior  time 
is  unquestionable. 

LIFE. 

The  earlier  part  of  Archaean  time  was  necessarily  without 
life;  for  until  the  rocks  and  seas  had  cooled  down  to  a  tem- 
perature below  that  of  boiling  water  (212°  F.)  life  was  not 
possible. 

Plants  of  the  lowest  orders  can  bear  a  higher  temper- 
ature than  the  lowest  of  animals,  and  therefore  were  prob- 
ably the  first  living  species.  Some  inferior  kinds  now  live 


LIFE.  143 

in  waters  having  a  temperature  of  150°  to  180°  F.,  which 
is  above  the  temperature  that  any  animal  life  can  bear. 
Much  evidence  from  fossils  as  to  the  life  is  not  to  be  looked 
for,  because  the  rocks  are  so  generally  metamorphic.  A 
supposed  fossil  Rhizopod  has  been  called  Eozoon,  from  the 
Greek  for  Dawn-life.  But  many  question  whether  the  speci- 
mens are  not  of  mineral  origin,  and  therefore  not  fossils. 
A  few  other  dubious  traces  of  fossils  have  been  reported  from 
some  of  the  less  metamorphic  Archaean  rocks.  But  probable 
evidence  of  plants  is  believed  to  be  afforded  by  the  great 
amount  of  graphite  in  some  beds.  Now  (1)  graphite  is 
nothing  but  carbon,  the  essential  principle  of  mineral  coal, 
and  (2)  mineral  coal  was  formed  from  plants ;  moreover  (3) 
mineral  coal  has  been  found  in  crystalline  rocks  converted 
into  graphite.  Here,  then,  is  probable  evidence  of  the  exist- 
ence of  plants.  Any  plants  present  were  probably  Sea- 
weeds, since  the  Cambrian  has  afforded  relics  of  no  plants 
but  Seaweeds.  Along  with  the  true  Seaweeds  there  were 
probably  Diatoms,  as  these  minute  species  are  among  the 
simplest  of  water-plants. 

The  occurrence  of  limestone  strata  is  also  thought  to  favor 
the  idea  of  the  presence  of  plants  or  animals,  since  the 
limestones  of  the  world  are  almost  all  of  organic  origin. 

Whenever  the  earliest  plant,  however  minute,  was  created, 
a  new  principle  was  introduced,  that  of  life,  which  is 
able  to  subordinate  physical  and  chemical  forces  to  its  uses, 
and  hold  them  at  service  until  death  occurs.  At  death, 


144  PALEOZOIC   TIME. 

chemical  forces  resume  their  ordinary  work  in  the  structure, 
and,  by  oxidation  and  other  processes,  destroy  it. 

Progress  in  a  system  of  life  becomes  from  this  time  the 
subject  of  highest  interest  in  the  world's  history. 

II.   PALEOZOIC   TIME. 

The  foundations  of  the  continents  and  their  outlines  having 
been  established  in  Archaean  time,  work  now  went  forward 
for  their  completion  through  further  rock-making.  The  rock- 
making,  as  has  been  explained,  was  the  work  of  the  waves  and 
marine  currents,  of  the  rivers  and  of  the  winds,  and  also  of 
quietly  acting  chemical  and  physical  agencies,  in  decomposing 
and  disintegrating  the  rocks  above  the  water's  level,  thus 
facilitating  the  work  of  the  waves,  rivers,  and  winds.  In 
addition,  living  species  were  early  in  the  seas,  and  contrib- 
uted, as  they  died,  shells  and  other  calcareous  relics  for  the 
formation  of  limestones. 

During  Paleozoic  time  the  greater  part  of  the  rocks  of  the 
eastern  half  of  North  America  were  completed;  and  by  the 
close  of  Mesozoic  time,  nearly  all  the  rest  had  been  made, 
and  the  great  Interior  seas  of  the  continent  had  become  dry 
land.  Afterward,  rock-making  was  carried  on  by  the  sea 
along  the  continental  borders,  and  also  over  the  Interior 
by  freshwater  agencies;  and  this  work  is  still  going  on. 

The  following  are  the  subdivisions  of  Paleozoic  time,  begin- 
ning with  the  lowest :  — 


CAMBRIAN   ERA.  145 


1.   EARLY  PALEOZOIC. 
1.    CAMBRIAN  era. 


(Reign  of  Trilobites. 

2.    LATER  PALEOZOIC. 

1.  UPPER   SILURIAN   era.  ") 

I  Reign  of  Fishes. 

2.  DEVONIAN  era.  J 

3.  CARBONIC   era.     Reign  of  Amphibians,  and  the  era 
of  coal-plants  or  Acrogens. 

1.    Early  or  Lower  Paleozoic. 

In  the  map  on  page  139  the  shaded  portion  of  the  continent 
was  probably  for  the  most  part  covered  with  water  at  the 
close  of  the  Archaean  era,  and  was,  therefore,  the  area  over 
which  the  earliest  Paleozoic  beds  may  have  been  laid  down. 
These  beds  were  mostly,  if  not  wholly,  marine ;  for  no  fresh- 
water deposits  or  fossils  have  yet  been  described  from  them. 

1.    Cambrian  Era. 

The  term  Cambrian  is  derived  from  the  old  name  of 
Wales.  The  Cambrian  era  is  divided  into  three  periods : 
(1)  EARLY  or  LOWER  CAMBRIAN  ;  (2)  MIDDLE  CAMBRIAN  ; 
and  (3)  LATER  or  UPPER  CAMBRIAN. 

ROCKS. 

The  areas  over  which  Cambrian  rocks  are  now  exposed 
to  view  border,  to  a  large  extent,  the  Archaean  lands.     The 
waves  worked  about  these  lands  and  there  made  the  sand, 
DANA'S  GKOL.  STORY  — 10 


146  PALEOZOIC   TIME. 

gravel,  and  finer  detritus  out  of  which  the  rocks  were  to  a 
large  extent  formed,  —  part  of  them  as  beach  deposits;  part 
as  beds  over  the  bottom  in  deeper  waters  wherever  detritus 
was  distributed  by  the  currents;  and  another  part  as  lime- 
stones. 

Many  of  the  sandstones,  as  the  Potsdam  sandstone,  in 
northern  New  York,  contain  worm  borings  like  those  made 
by  sea-worms  in  modern  sandy  shores  (Fig.  149,  page  152). 
Ripple-marks  sometimes  cover  the  layers,  and  footprints 
or  trails  of  animals  are  occasionally  met  with.  These  bur- 
rows and  markings  are  evidence  that  the  rocks  were  made 
in  shallow  water  or  along  beaches;  that  the  work  of  rock- 
making  was  slow  and  quiet  work,  just  like  that  along  shal- 
low sea-borders  of  the  present  day;  and  also,  that  in  the 
Cambrian  era  the  tides  and  currents  of  the  sea  were  no 
more  powerful  than  now.  None  of  the  beds,  so  far  as  has 
been  found,  bear  positive  evidence  of  deep-sea  origin. 

The  beds  occur  in  northern  New  York  at  the  east  foot 
of  the  Adirondack  Mountains  (which  are  Archaean)  and 
along  the  borders  of  the  Canadian  Archaean ;  along  the 
Taconic  range  in  eastern  New  York  and  western  New  Eng- 
land; in  the  Appalachian  region  at  intervals  from  New 
York  to  Alabama;  near  the  Archaean  of  Wisconsin  and 
Minnesota ;  in  some  parts  of  the  Rocky  Mountain  region ; 
and  as  far  west  as  the  Sierra  Nevada,  in  California.  Far 
the  larger  part  of  the  beds  made  in  Cambrian  time  are  now 
buried  beneath  the  later  formations. 


CAMBRIAN    ERA.  147 

Sandstones  occur  among  the  deposits  of  each  of  the  Cam- 
brian periods,  and  so  do  limestones.  The  Potsdam  sand- 
stone, at  the  foot  of  the  Adirondacks,  belongs  to  the  Upper 
or  Later  division.  Limestones  of  the  Early  Cambrian  out- 
crop in  northern  Vermont  and  in  many  other  regions.  The 
great  magnesian  limestone  of  Missouri  and  some  Other  por- 
tions of  the  Mississippi  Valley  is  in  part  Cambrian.  In 
some  regions  that  are  now  mountain  regions  the  thickness 
of  the  Cambrian  rocks  is  great,  exceeding  in  some  places 
20,000  feet. 

In  Great  Britain  Cambrian  rocks  are  found  in  western 
Scotland  and  England,  and  in  Wales  and  Ireland. 

LIFE. 

The  seas  of  the  Early  Cambrian,  although  the  earliest  of 
Paleozoic  time,  abounded  in  life. 

The  plants,  as  far  as  shown  by  fossils,  were  all  Seaweeds. 
There  were  perhaps  Lichens  over  the  dry  rocks  of  the  land, 
but  no  traces  of  them  have  yet  been  found. 

The  animals  of  which  remains  have  been  found  are  all 
marine.  The  species  include  Sponges  (Fig.  128)  and  Corals 
(Figs.  129-131);  and  there  can  be  no  doubt  that  the  Corals 
when  alive  were  as  beautiful,  in  their  flower-like  form  (page 
43)  and  color,  as  those  of  modern  seas.  There  were  also 
Crinoids,  the  primitive  type  of  Echinoderms,  having  stems 
like  plants  (page  46).  Fig.  129,  on  page  148,  representing  one 
of  the  Corals,  shows  the  interior  partly  filled  with  the 


148 


PALEOZOIC   TIME. 


rock  in  which  the  specimen  lay  buried.  Fig.  130  is  a  side- 
view  of  an  imperfect  specimen  of  another  Coral,  and  Fig. 
131  a  cross-section  of  the  same. 


FIGS.  128-131. 


Sponge;  Corals. 

Fig.   128,  SPONGE:  Leptomitus    Zittelli;    Figs.    129-131,    CORALS:    129,   Archwocyathus 
profundus;  130,  131,  Spirocyathus  Atlanticus. 

Other  common  species  were  the  Molluscoids  of  the  division 
of  Brachiopods  (Figs.  132  to  134),  the  most  abundant  of  all 
Paleozoic  fossils. 

There  were  also  Mollnsks,  of  which  three  grand  divisions 
were  represented,  —  that  of  Lamellibranchs  or  "Bivalves"; 
of  Gastropods  or  Univalves  (Figs.  136,  137,  the  former  of 
a  kind  much  like  a  limpet);  and  of  Pteropods  (Fig.  138). 


CAMBRIAN   ERA. 


149 


FIGS.  132-134.        132  a. 


Brachiopods. 


The  Lamellibranchs  and  Gastropods  were  few  in  species  and 
very  small ;  but  the  Ptero- 
pods  were  very  abundant 
and  of  much  larger  size  than 
any  now  existing.  More- 
over, some  species  had  a  lid, 
called  an  operculum  (Fig. 
138  a),  for  closing  the  open 
end  of  the  shell;  and  in 
this  respect  were  superior  to  Flg 

modern  kinds  (Fig.  119).  (Billingsella)  festinata. 

Worms  are  somewhat 
doubtfully  represented 
by  their  tracks  and  bur- 
rows. The  Crustaceans 
were  represented  by 
Trilobites,  the  highest 
life  of  the  Cambrian 
world.  The*  name  al- 

^%^jk"  '^Jij^  ludes  to  the  three  lon- 

gitudinal divisions  into 
which  the  body  is  ap- 
parently divided.  Fig. 
139  represents,  natural 
size,  a  species  of  the  Early  Cambrian.  In  Figs.  140  and 
141  the  forms  of  other  Crustaceans  are  shown,  the  latter 
one  of  the  Ostracoid  or  bivalve  kind. 


Mollusks. 

Fig.  135,  LAMELLIBRANOH  :  Fordilla  Troyensis;  Figs. 
136,  137,  GASTROPODS  :  136,  Stenotheca  rugosa ; 
187,  Platyceras  prima-vum  ;  Fig.  138,  PTEROPOD  : 
Hyolithes  Americanus ;  138  a,  operculum  of 


150 


PALEOZOIC   TIME. 


The   two   higher   subdivisions  of   Crustaceans   are   the   10- 
footed    (or    Decapods,    as    Crabs,    Shrimps,    etc.)    and    the 


139. 


FIGS.  139-141. 


140. 


Trilobite. 

Olenellus  Vermontanus. 


Phyllopod    and    Ostracoid 
Crustaceans. 

Fig.  140,  PHYLLOPOD  :  Protocaris  Mar- 

shi ;  Fig.  141,  OSTRAOOID  :  Aris- 

tozoe  rotundata. 

FIGS.  142,  143. 
142  143 


Modern  Tetradecapod 

Crustaceans. 
Fig.    142,    Scrolls  (x  J); 
143,  Porcellio. 


14-footed  (or  Tetradecapods,  as  the  Sow-bugs  and  Sand-fleas). 
The  Trilobites  are  most  nearly  related  to  the  latter,  and  to 
that  division  of  the  14-footed  species  called  Isopods,  illus- 
trated in  Figs.  142,  143. 


CAMBRIAN    ERA. 


151 


In  the  Middle  and  Later 
already  mentioned,  were  con- 
tinued, and  one  new  class  un- 
der Mollusks  was  added,  tha.t 
of  the  Cephalopoda.  But  the 
species  found  as  fossils  are 
nearly  all  different  from  those 
of  the  Early  Cambrian.  There 
were  other  Trilobites  of  va- 
rious genera.  One  of  the 
larger  kinds,  from  Braintree, 
near  Boston,  is  represented  in 
Fig.  144;  it  was  ten  inches 
long;  another,  of  the  same 
genus,  from  New  Brunswick, 
had  a  length  of  fifteen  inches 
and  a  breadth  of  eleven. 
Thus  these  Crustaceans  were 

145  FIGS.  145-148. 


Cambrian   periods   the   groups 


FIG.  144. 


Brachiopods ;  Gastropod . 
Figs.  145-147,  BBACHIOPODS:    145,    146,   Lin- 
gulella  priuia  (x  1) ;   147,  Lingulepis  anti- 
qua;  Fig.  148,  GASTROPOD  :  Holopea  Sweeti. 


Trilobite. 

Paradoxides  Hurlani  (x  J). 

almost  as  large  as  the 
largest  of  modern  species, 
while  the  Mollusks  that  ap- 
peared in  the  Early  Cambrian 
were  all  very  small  species. 

Figs.  145-148  represent  a 
few  fossils  of  the  Upper 
Cambrian.  Figs.  145,  146, 
147  are  shells  of  Brachio- 


152 


PALEOZOIC   TIME. 


pods  called  Lingulella  and  Lingulepis,  from  the  Latin  lingua, 
tongue. 

The  evidences  of  Worms  in  the  Cambrian,  and  also  through 
later  time,  are  commonly  either  borings  which  are  now  filled 
with  sandstone  (Fig.  149),  or  the  trails  or  tracks  left  on  mud- 
beds  by  the  crawling  Worm  (Fig.  150). 


FIGS.  149,  150. 


Worm-borings  and  Trails. 

DISAPPEARANCE  OF  SPECIES. 

The  long  Cambrian  era  closed,  in  eastern  North  America, 
without  the  intervention  of  a  time  of  upturning  or  moun- 
tain-making to  mark  the  interval  between  it  and  the  following 
Lower  Silurian  era.  The  transition  was  gradual,  the  later 
beds  overlying  the  earlier  without  marked  unconformability. 
Still  very  few  of  the  Cambrian  species  are  known  to  occur 
in  Lower  Silurian  beds.  Moreover,  very  few  species  are 
known  to  pass  up  from  the  Lower  Cambrian  to  the  Middle 
Cambrian,  or  from  the  Middle  to  the  Upper  Cambrian. 


LOWER   SILURIAN   ERA.  163 

2.   Lower  Silurian  Era, 

The  Lower  Silurian  era  is  divided  into  two  periods:    (1) 
the  CANADIAN  and  (2)  the  TRENTON. 

ROCKS. 

The    rocks  of    the    Lower    Silurian    era    are    to  a  large 
extent  limestones. 

1.  Canadian  Period. —  During  the  earlier  of  the  two  periods, 
the  "calciferous   sandstone"  was  formed  along  the  borders 
of  the  Archaean  lands  in  northern  New  York  —  a  rock  mostly 
without  fossils.     This  was  followed  by  the  "  Chazy  limestone," 
which  occurs  at  Chazy,  on  the  west  side  of  Lake  Champlain  and 
in  western  Vermont,  and  is  in  some  places  abundantly  fossilif- 
erous.     The  St.  Peter's  sandstone  of  Iowa  has  been  supposed 
to  be  of  the  age  of  the  Chazy  limestone ;  but  this  is  doubtful. 

2.  Trenton  Period. —  The  Trenton  period  is  represented  by 
the   Trenton  limestone,   a   great   limestone   formation  which 
occurs  widely  over  North  America,  both  along  the  Appalachian 
border   of  the   continent   and   throughout   its   interior.     The 
Trenton    period    is    the    most     extensive     limestone-making 
period  in  the  world's  history.     The  limestone  indicates  that 
the   waters   over  the    Continental   area   were   generally   free 
from   sediment,   but   not   that   they   were    deep    waters,   for 
modern   coral  reefs  are  formed  of   corals  and  shells  within 
100  yards  of  the  surface. 

The   Trenton   limestone   was   named   from   Trenton   Falls, 
on  West  Canada  Creek,  near   Utica,  New  York,  where  the 


154  PALEOZOIC   TIME. 

gorge   is   cut  through   it.     The  Galena  or  lead-bearing  lime- 
stone  of  Illinois   and   Wisconsin   is   Upper   Trenton. 

Finally,  in  the  later  part  of  the  Trenton  period,  lime- 
stone-making was  confined  almost  wholly  to  the  interior 
region ;  for  the  Appalachian  area,  including  New  York,  was 
receiving  fragmental  deposits  as  shales,  sandstones,  and 
conglomerates;  and  out  of  the  niud-beds  the  Utica  shales 
and  Hudson  shales  were  made  at  this  time.  They  indi- 
cate some  shallowing  of  the  waters  so  that  muddy  sedi- 
ments were  taken  up  and  widely  distributed. 

In  Great  Britain,  the  Lower  Silurian  has  at  base  slates 
and  sandstones  of  the  Arenig  series.  Above  them  are  the 
Llandeilo  flags  and  the  Bala  group,  corresponding  nearly  to 
the  Trenton  period.  The  thickness  in  Wales  is  stated  to  be 
25,000  feet. 

LIFE. 

The  seas  abounded  in  life.  The  plants  thus  far  found  in 
North  America  are  all  Seaweeds ;  but  remains  supposed  to  be 
those  of  land  plants  occur  in  Great  Britain,  which  show  that 
the  hills  and  plains  were  already  green.  One  of  the  Seaweeds 
is  represented  in  Fig.  151 ;  and  in  Fig.  152,  a  supposed 
land  plant,  near  the  modern  Horsetail  or  Equisetum  in 
its  character.  Nodules  of  coal  occur  in  one  of  the  forma- 
tions, which  are  supposed  to  have  come  from  buried  Sea- 
weeds, or  else  from  animal  material,  or  from  mineral 
oil  that  has  been  derived  from  the  decomposition  of  plants 
or  animals. 


LOWER    SILURIAN   ERA. 


155 


The  animals  are  chiefly  marine  Invertebrates,  as  in  the  Cam- 
brian.    But  before  the  close  of  the  Trenton  period  there  were 

FIGS.  151,  152.  152 


Seaweed;  Land -plant  (supposed). 

Fig.  151,  SEAWEED.     Buthotrophis  gracilis  ;  Fig.  152,  LAND  PLANT  (supposed): 
Protannularia  Harknessi. 

also  Fishes,  marine   Vertebrates,  and  the  earliest  known  of 
Insects. 

Among    Protozoans    there    were    Rhizopods   and  Sponges. 

FIGS.   153,  151. 


Polyp  Corals. 

Fig.  158,  Streptelasma  corniculum  ;  154,  Columnaria  alveolate  ;  154  a, 
top  view  of  same. 

The  Radiates  included  Corals,  Crinoids,  and  Starfishes. 
Fig.  153  is  a  side-view  of  one  of  the  conical  Corals  of  the 
Trenton  limestone;  the  top  has  a  cup-like  cavity  radiated 


156 


PALEOZOIC    TIME. 


with  calcareous  plates,  somewhat  like  Fig.  15,  page  45; 
and  the  living  polyp  must  have  much  resembled  that  of 
Fig.  16,  except  that  it  was  circular. 

Another  Coral,  honeycomb-like  in  its  columnar  structure, 
and  hence  named  Columnaria,  is  represented  in  Fig.  154.  The 
cells  are  radiated,  as  shown  in  the  figure,  but  in  a  vertical  sec- 

FHJS.  155-158. 


Crinoids;  Ophiuroid;  Asterioid. 

Figs.  166, 166,  CRINOIDS  :  155,  Pleurocystites  fllitextus ;  156,  Taxoerinus  elegans ;  Fig.  157, 
ASTERIOID  :    Palseaster  matutinus ;  Fig.  158,  OPHIUROID  :  Ta-niaster  spinosus. 

tion  (as  seen  in  such  a  section  of  one  of  the  cells  in  Fig.  154) 
the  cells  are  crossed  by  horizontal  partitions.  The  cora)  has 
been  found  in  masses  several  feet  in  diameter.  It  had  flower- 
like  animals  similar  to  those  of  Fig.  14,  but  smaller. 

Figs.  155-158  represent  some  of  the  Crinoids  and  Star- 
fishes. Fig.  156  is  a  Crinoid  from  the  Trenton  limestone, 
though  not  a  perfect  one,  as  the  arms  are  broken  off  at  the 
tips,  and  the  stem  below  (by  which  it  was  attached  to  the  rock 


LOWER    SILURIAN   ERA. 


157 


of  the  sea-bottom,  and  which  may  have  been  several  inches 
long)  is  mostly  wanting.  Fig.  155  shows  the  form  of  another 
kind  of  Crinoid,  one  of  very  irregular  shape,  called  a  Cystid, 
from  the  Greek  for  hladdn:  Its  stem,  when  it  was  living,  was 
run  down  into  the  inud  of  the  sea-bottom,  instead  of  being 
attached  to  a  rock.  The  arrangement  of  plates  on  the  body 
is  irregular,  and  it  has  only  two  arms.  Figs.  157,  158  are 
two  of  the  Starfishes  of  the  ancient  seas. 


ico 


Brachiopods. 
Fig.  159,  Leptona  sericea  ;  160,  Orthis  occidental  ;  161,  O.  biforata  ;  162,  O.  testudinaria. 

Brachiopods  were  very  numerous.  Some  of  them  from  the 
Trenton  limestone  are  represented  in  Figs.  159  to  162.  Bry- 
ozoans  also  were  abundant. 

The  earliest  species  of  Cephalopods  had  straight  shells,  like 
that  of  a  Nautilus  (page  131)  straightened  out,  —  whence  the 
name  Orthocems,  meaning  a  straight  horn.  One,  from  the 
Trenton  limestone,  is  represented  in  Fig.  163 ;  it  has  partitions 
like  those  in  the  shell  of  the  Nautilus. 

In  the  Orthoceras,  as  in  the  Nautilus,  a  tube  called  the 
siphunde,  meaning  little  siphon,  passes  from  the  outer  chamber 
through  the  partitions  and  all  the  chambers ;  and  the  hole  in 


158 


PALEOZOIC   TIME. 


one  of  the  partitions  is  shown  in  Fig.   lfi.3  a.     There  were  also 
coiled  species  of  the  group,  in  the  Trenton  formation. 


Cephalopod . 
Orthoceras  junceum. 

The  Articulates  included  Worms  and  Crustaceans,  as  in 
Cambrian  time.  One  of  the  large  Trilobites,  an  AsapJms,  is 
represented  in  Fig.  164;  its  length  was  abouj  8  inches. 

FIGS.  164-166. 

165 
1U 


165  a 


Trilobites. 

Fig.  164,  Asaphus  platycephalus ;   165  a,  Calymene  callicepbala ;   166,  Triarthnis  Beckil, 
the  specimen  showing  the  legs. 

Another  common  species,  a  Calymene,  is  shown,  reduced  to 
half  the  natural  size,  in  Fig.  165.  It  is  often  found  rolled 
into  a  ball  (Fig.  165  a).  Another  species  from  the  Utica  slate, 


OBSERVATIONS   ON    THE   EARLY   PALEOZOIC.          159 

a  Triartlirm,  is  represented  in  Fig.  166;  it  shows  that 
Trilobites  had  legs,  although  the  specimens  from  most  local- 
ities show  none.  There  were  also  many  species  of  Ostracoids, 
or  Bivalve  Crustaceans. 

The  Insects  of  the  Trenton  period  are  known  thus  far 
only  from  two  specimens,  one  found  in  Sweden,  and  one  in 
France.  As  both  are  well  authenticated,  it  is  safe  to  con- 
clude that  Insects  were  in  great  numbers  over  the  land  of 
all  the  continents.  It  is  probable  also  that  the  land  had 
its  Myriapods,  although  the  first  specimen  has  not  yet  been 
found.  Insects  are  little  likely  to  become  buried  in  marine 
deposits.  Coming  within  reach  of  the  seashore  waves,  they 
would  at  once  be  ground  \ip. 

The  earliest  remains  of  Vertebrates  have  been  found  in 
Trenton  rocks  of  Colorado.  They  are  chiefly  bony  scales 
from  the  covering  of  Fishes.  They  are  related  to  those 
found  in  rocks  of  the  Upper  Silurian  and  Devonian  eras. 
(See  pages  169,  179.) 

Observations  on  the  Early  Paleozoic. 

1.  Life.  —  The  life  of  the  Early  Paleozoic,  as  the  preced- 
ing review  shows,  was  almost  all  marine.  It  was  made  up 
largely  of  the  best  of  limestone-makers,  that  is,  species 
which  secrete  a  large  amount  of  lime  carbonate,  —  as  the 
Crinoids,  species  consisting  chiefly  of  calcareous  disks ;  Bryo- 
zoans,  which  are  as  much  stone  as  the  Crinoids;  Brachio- 
pods,  which  have  thick  calcareous  shells ;  and  Corals.  These 


160  PALEOZOIC    TIME. 

kinds  owe  their  fine  preservation  as  fossils  to  their  calca- 
reous skeletons.  Other  kinds,  like  Worms,  and  shell-less 
Mollusks  and  K-adiates,  of  which  there  were  doubtless  great 
numbers,  left  no  record  of  themselves. 

The  early  species  were  largely  stationary  life,  that  is, 
were  attached  to  the  sea-bottom  or  some  support.  Such 
were  all  the  Crinoids,  Bryozoans,  and  Corals,  and  most  of 
the  Brachiopods.  Moreover,  some  Mollusks,  as  the  Mussels, 
live  attached  to  rocks  through  life  by  a  byssus  of  horny 
threads.  The  locomotive  species  were  the  Trilobites,  Gas- 
tropods, Orthocerata  and  related  Cephalopods,  and  the 
Fishes.  The  Cephalopods  may  have  added  much  to  the 
activity  of  the  seas;  for  the  species  are  not  snail-like  in 
pace,  like  Gastropods,  but  are  fleet  movers,  like  Fishes.  Yet 
these  ancient  species,  with  their  unwieldy  shells,  must  have 
been  slow  compared  with  the  naked  Cephalopods  of  later 
time,  and  therefore  easy  game  for  the  Fishes. 

2.  Mineral  Oil  and  Gas.  — A  large  amount  of  mineral  oil  and 
gas  is  afforded  in  some  regions  by  the  Trenton  formation 
and  chiefly  the  limestone.  At  Findlay,  and  some  other 
places  in  Ohio,  borings  are  made  to  a  depth  of  several 
hundred  feet,  through  the  overlying  rocks,  and  then  for  10 
to  50  feet  into  the  limestone;  the  gas  comes  up  with  a 
rush  and  continues  to  escape  for  years.  From  one  boring 
over  a  million  cubic  feet  of  gas  have  been  obtained  per 
day.  The  gas  is  used  both  for  lighting  houses  and  for  fuel. 
In  other  cases  oil  is  obtained,  which  when  purified  becomes 


OBSERVATIONS    ON   THE   EARLY   PALEOZOIC.          161 

kerosene.  The  oil  and  gas  have  nearly  the  same  composi- 
tion, differing  little  from  that  of  common  burning  gas. 
They  were  produced  by  the  decomposition  of  the  animal  or 
vegetable  substances  in  the  rock,  afforded  by  the  dead  plant 
or  animal  life  of  the  seas. 

MOUNTAIN-MAKING. 

The  close  of  the  Early  Paleozoic,  that  is,  of  the  Trenton 
Period,  was  a  time  of  upturning  and  mountain-making  in 
North  America,  Great  Britain,  and  Europe.  The  Taconic 
Mountains  were  then  made,  a  range  500  miles  long,  extending 
along  the  western  and  northwestern  border  of  New  Eng- 
land, from  Canada  to  northwestern  Connecticut  and  Put- 
nam County  in  eastern  New  York. 

The  rocks  —  which  originally  included  much  limestone, 
and  also  various  fragmental  rocks,  shales,  sandstones,  and  con- 
glomerates overlying  and  underlying  the  limestone  —  were 
pressed  up  into  folds;  and  at  the  same  time  they  were  crys- 
tallized by  the  heat  produced  by  the  upturning,  and  thus 
changed  to  metamorphic  rocks.  The  fossiliferous  limestone 
was  altered  to  white  and  clouded  crystalline  or  archi- 
tectural marble,  (of  which  Canaan  in  Connecticut,  Lee  in 
Massachusetts,  and  Rutland  in  Vermont  afford  noted  exam- 
ples) ;  the  quartzose  sand-beds,  to  quartzyte ;  the  mud-beds 
and  shales  to  gneiss,  mica  schist,  and  other  crystalline  rocks. 
The  upturned  beds  that  were  then  made  into  a  mountain 
range  include  all  of  the  Early  Paleozoic  formations  from 
DANA'S  GEOL.  STORY  — 11 


162  PALEOZOIC   TIME. 

the  bottom  of  the  Cambrian  to  the  top  of  the  Lower  Silurian,  and 
probably  had  a  thickness  in  some  parts  exceeding  20,000  feet. 
As  described  for  the  Appalachian  range  on  pages  114,  203, 
these  beds  were  laid  down  over  a  gradually  subsiding  area, 
and  the  syncline  or  trough  had  a  depth  equal  to  the  thick- 
ness of  20,000  feet.  Thus  the  material  for  the  mountain 
range  was  first  deposited;  and  then  the  range  was  made  out 
of  this  prepared  material.  In  the  West,  where  there  was 
no  mountain-making  at  this  era,  in  Illinois  the  thickness 
of  the  Cambrian  and  Lower  Silurian  rocks  is  only  800  feet, 
and  in  Missouri  only  2200  feet. 

It  is  probable,  also,  that  another  Taconic  mountain  range 
was  formed  at  the  same  time,  commencing  in  the  eastern  part 
of  Canaan,  Connecticut,  and  continuing  southward  through 
Westchester  County,  New  York,  to  Manhattan  Island;  and 
still  another,  if  not  a  continuation  of  the  last,  from  the 
vicinity  of  Philadelphia  to  Buckingham  County,  Virginia 
(where  the  crystalline  rocks  have  afforded  fossils),  and  beyond 
this  southwestward.  The  Taconic  revolution,  in  this  view, 
left  its  marks  in  mountains  and  in  crystalline  rocks  along  the 
whole  Atlantic  border,  and  the  two  or  three  Taconic  moun- 
tain ranges  constitute  together  a  long  Taconic  mountain 
system. 

Moreover,  a  large  part  of  this  Atlantic  border  was  simul- 
taneously lifted  above  the  sea  level.  This  is  proved  by  the 
fact  that  along  this  border  south  of  New  York  no  marine 
deposits  are  known,  either  of  the  Upper  Silurian,  or  of 


LATER   PALEOZOIC.  163 

any  following  formation  earlier  than  the  Cretaceous,  the 
last  period  of  the  Mesozoic. 

In  Great  Britain  the  Lower  Silurian  formations,  which  are 
throughout  conformable,  are  upturned  so  as  to  lie  uncon- 
formably  beneath  the  beds  of  the  next  era — the  Upper 
Silurian. 

The  elevation  of  the  AVestmoreland  Hills,  of  the  moun- 
tains in  North  Wales,  and  of  the  range  of  Southern 
Scotland  from  St.  Abb's  Head,  on  the  east  coast,  to  the 
Mull  of  Galloway,  has  been  referred  to  this  era.  The  max- 
imum thickness  of  the  Lower  Silurian  rocks  of  Britain 
has  been  stated  to  be  over  40,000  feet. 

2.    Later  Paleozoic. 

It  is  stated  above  that  a  large  part  of  the  Atlantic  border 
of  North  America  was  raised  above  the  sea  level  at  the  time 
of  the  Taconic  revolution.  The  ocean's  waves  and  currents 
had  had  full  sweep  over  this  border  in  the  Early  Paleo- 
zoic, and  had  aided  much  in  rock-making.  Till  now,  the 
whole  continent  had  been  one  great  Continental  sea,  with 
a  few  islands  over  its  surface.  But  the  uplift  placed  a 
barrier  to  the  Atlantic  Ocean  on  the  east,  which  extended 
south  nearly  to  the  Florida  boundary;  and  after  this  epoch, 
in  Later  Paleozoic  time,  the  waters  of  the  Continental  In- 
terior behind  this  barrier  had  to  do  their  geological  work 
without  Atlantic  aid.  To  the  westward,  these  waters  ex- 


164 


PALEOZOIC    TIME. 


tended  to  the  Pacific.    To  the  southward  there  was  complete 
connection,  as  before,  between  the  Atlantic  and  Pacific. 

This  eastern  barrier  of  the  continent  is  shoAvn  on  the 
map,  Fig.  167.  The  Gulf  of  St.  Lawrence  was  still  outside 
the  barrier,  and  marine  channels  or  bays  extended  down 
from  it  over  New  England;  but  dry  land  made  the  barrier 
complete  between  New  York  and  Canada. 

FI.I.  107. 


North  America  at  the  Opening  of  the  Later  Paleozoic. 

1.     Upper  Silurian  Era. 

The  era  of  the  Upper  Silurian  is  divided  into  three  periods. 
Beginning  with  the  earliest,  they  are:  (1)  the  NIAGARA, 
(2)  the  (KnNDAiiA,  and  (3)  the  LOWER  HELDKBBEI;*;. 


UPPER   SILURIAN   ERA.  165 

ROCKS. 

1.  Niagara  Period.  —  This  period  is  especially  noted  for  its 
great  fossilii'erous  limestone  formation.  It  was  named  from 
its  occurrence  at  Niagara  Falls.  The  Niagara  formation 
at  Niagara  River  and  elsewhere  in  western  New  York, 
and  also  along  the  region  of  the  Appalachians,  includes, 
Jirat,  a  thin  laminated  sandstone  stratum,  called  the  Medina 
sandstone;  second,  other  sandstones  associated  with  shales 
and  limestones,  the  Clinton  group,  in  which  occurs,  in  many 
localities,  a  bed  of  red  iron  ore ;  third,  the  Niagara  shale 
and  limestone,  the  strata  at  Niagara  Falls,  where  the  upper 
80  feet  are  limestone  and  the  lower  80  feet  shale.  Niagara 
shale  has  little  extent  to  the  west  of  New  York,  while  the 
limestone  spreads  very  widely,  reaching  into  Iowa  and 

Tennessee. 

The  layers  of  the  Medina  sandstone  often  have  ripple- 
marks,  mud-cracks,  wave-marks,  and  other  evidences  of  mud- 
flat  or  sand-flat  origin,  showing  that  central  and  western 
New  York,  with  the  region  to  the  southwest,  was  then  an 
area  of  great  mud  and  sand  flats;  but  later  these  interior 
waters  were  more  open  and  clearer;  so  that  there  was  less 
sediment,  and  the  life  required  for  making  limestone  flourished. 

In  Great  Britain  the  Wenlock  shale  and  limestone  are  of 
the  age  of  the  Niagara  shale  and  limestone.  They  are  in 
view  between  Aymestry  and  Ludlow,  near  Dudley,  and  else- 
where. The  limestone,  like  the  Niagara,  is  fidl  of  fossils. 


166  PALEOZOIC    TIME. 

2.  Onondaga  Period.  —  This  period  is  noted  for  its  salt  de- 
posits.    Its  clayey  rocks,  without  fossils,  and  its  salt  show  that 
central   New   York,  and  the  borders  of  Canada  to  the  west, 
with  part  of  Ohio,  were  then  the  site  of  great  salt  basins, 
where   sea-water   evaporated,   impregnating  the   mud   of   the 
shallow  sea  with  salt,  or  making  deposits  of  rock  salt.    The 
brines   of   Salina  and   that   vicinity   in   New  York   are  salt- 
water wells,  obtained  by  boring  down  to  this  saliferous  rock. 
But  farther  south   and   west  in  New  York  and  at  Goderich 
in  Canada,  and  also  near  Cleveland,  in  Ohio,  there  are  beds  of 
rock  salt,  some  of  them  40  to  80  feet  thick. 

In  the  Ouondaga  formation,  and  in  the  overlying  Lower 
Helderberg,  there  occur  occasionally  large  local  beds  of  gyp- 
sum, or  calcium  sulphate.  Part  of  these  beds,  if  not  all, 
were  made  by  the  action,  on  beds  of  limestone,  of  waters 
holding  sulphuric  acid.  Some  of  them  may  be,  like  the 
salt-beds,  the  direct  result  of  the  evaporation  of  sea-water. 
There  are  many  sulphur  springs  in  the  western  part  of 
New  York,  whose  waters  give  out  sulphuretted  hydrogen 
(or  hydrogen  sulphide)  which  were  produced  by  the  decom- 
position of  minerals  containing  sulphur  in  the  rocks  below; 
and  not  unfrequently  sulphuric  acid  has  resulted  from  the 
oxidation  of  the  sulphuretted  hydrogen,  making  acid  springs. 

3.  Lower  Helderberg  Period.  —  This  period,  which  followed 
the  Onondaga,  was  noted  for  a  return  of  the  conditions  required 
for  making  fossiliferous  limestone,  showing  that  the  waters  had 
deepened  over  New  York,  especially  to  the  eastward,  that  the 


UPPER    SILURIAN   ERA.  167 

salt-making  basins  had  consequently  disappeared,  and  that 
once  more  there  were  clearer  waters  and  abundant  life.  The 
name,  Loiver  Helderberg,  is  from  the  Helderberg  Mountains, 
southwest  of  Albany,  where  the  beds  occur. 

The  formation  thins  out  to  the  westward  in  New  York, 
being  thickest  in  the  vicinity  of  the  Hudson  Eiver  valley. 
Moreover,  it  appears  east  of  the  river  in  Becrafts  Moun- 
tain near  Hudson,  and  probably  extended  northward  to  the 
St.  Lawrence;  for  rocks  of  the  period  are  found  near 
Montreal.  They  appear  to  be  evidence,  therefore,  that 
although  the  Avaters  of  the  St.  Lawrence  Bay  were  cut  off 
from  those  of  New  York  during  the  Niagara  and  Onon- 
daga  periods,  the  two  were  connected  temporarily  during 
this  last  period  of  the  Upper  Silurian.  The  beds  also 
extend  southwestward  along  the  Appalachians. 

Following  the  Wenlock  group  in  Great  Britain  there  is 
the  Ludlow  group,  consisting  of  sandstones,  shales,  and  the 
Aymestry  limestone,  corresponding  in  age  with  the  later 
part  of  the  American  Upper  Silurian. 

LIFE. 

1.  Plants. — The  first  American  species  of  land  plants 
have  been  obtained  from  beds  of  the  Upper  Silurian.  The 
species  were  not  Mosses,  nor  Grasses,  but  species  of  the 
Ground  Pine  tribe  or  Lycopods,  the  hiyJiest  division  of  Crypto- 
gams. They  are  described  beyond,  in  the  account  of  the 
Devonian  plants. 


168 


PALEOZOIC    TIME. 


2.  Animals.  —  Among  the  animals  of  the  era  there  was  the 
same  preponderance  of  Corals  and  Crinoids  among  Radiates, 
of  Brachiopods  and  Bryozoans,  and  of  Trilobites  among  Crns- 

FIGS.  1CS-170.  170 

169 


Corals;  Crinoid. 

Figs.  168,  169,  CORALS:  168,  Zaphrentis  bilateralis ;  169,  Halysites  catennlatus ;  Fig.  1TO, 
Cr.iNDiD :  Iclitliyocrinus  loevis. 

taceans,  as  in  the  Lower  Silurian.     There  were  also  Fishes  in 
the  seas;  and  Scorpions,  as  well  as  Insects,  over  the  hmd. 
A   few    figures    of    Invertebrates    are    here    given.     Figs. 

FIOB.  171-178. 

173 


Brachiopods. 

Fig.   171,   Leptaena  rhomboidalis ;    172,   side  view   of  Spirifer  Niagarensis  ;    173,  Orthis 
biloba;   173  a,  enlarged  view  of  same. 

168,  109,  represent  two  of  the  Corals  of  the  Niagara  period ; 
Fig.  168,  related  to  the  Coral  of  the  Lower  Silurian,  shown 
in  Fig.  153;  Fig.  169,  a  Coral  imbedded  in  limestone,  which 


UPPER   SILURIAN  ERA. 


169 


looks,  in  a  section  of  the  limestone,  a  little  like  a  chain,  or 
a  string  of  links,  and  has  hence  been  called  Chain-coral. 
Fig.  170  represents  one  of  the  Niagara  Crinoids. 

Some  of  the  common  Brachiopods  of  the  Niagara  group 
are  represented  in  Figs.  171-173. 

The  following  are  figures  of  two  of  the  larger  Trilobites. 
Both  figures  are  reduced  views,  Fig.  174  being  but  one  third 
the  natural  length,  and  Fig.  175  one  fourth. 


FIGS.  174,  175. 


Trilobites. 
Fig.   174,  Lichas   Boltoni  (xj);   175,   Homalonotus  delphinocephalua  (x  J). 

Of  Insects  only  Cockroaches  have  yet  been  found.  But 
these  species  had  a  better  chance  of  preservation  than 
most  others  because  they  frequent  damp  places;  and  this  is 
a  good  reason  for  the  survival  of  their  remains. 

Eemains  of  Fishes  have  been  found  in  the  Onondaga 
beds.  They  are  of  the  kind  called  Placoderms,  having  the 
anterior  part  of  the  body  covered  with  bony  plates,  as  illus- 


170  PALEOZOIC   TIME. 

trated  in  Fig.  176.  Placoderms  were  common  also  in  the 
Devonian.  Remains  supposed  to  be  those  of  Fishes  have 
also  been  found  in  the  Clinton  division  of  the  Niagara.  In 
England,  Upper  Silurian  beds  contain  remains  of  Fishes 
related  to  the  Sharks,  and  to  the  Ganoids.  Ganoids  differ 
from  most  modern  Fishes  in  having  bony  scales  or  plates 
(Figs.  191-193).  A  few  species  are  now  living  in  Ameri- 
can rivers  and  lakes.  The  living  species  of  the  seas,  as  the 
transitions  in  the  fossils  of  the  successive  beds  show,  con- 
tinued to  change  through  the  Upper  Silurian  era  as  well  as 
through  the  Lower  Silurian;  that  is,  the  species  of  the  early 
part  had  nearly  all  disappeared  and  new  species  had  be- 
come substituted  before  the  later  part  of  the  era  began; 

FIG.  1T6. 


Placoderm  Fish. 

Restoration  of  Pala-aspis  Americana. 

and  each  of  the  successive  subdivisions  in  the  rocks  indi- 
cates some  old  feature  lost  during  its  progress  or  in  the 
transition,  and  some  new  feature  gained.  The  transition 
from  the  Upper  Silurian  to  the  Devonian  era  was  gradual. 

2.    Devonian  Era. 

The  term  Devonian  was  first  applied  to  the  rocks  of  the 
era  in  Great   Britain  by   Sedgwick   and  Murchison,  and  al- 


DEVONIAN   BRA.  171 

lucles  to  the  region  of  South  Devon,  where  the  rocks  occur 
and  abound  in  fossils.  The  era  is  divided  into:  (1)  the 
EARLY  or  LOWER  DEVONIAN,  (2)  the  MIDDLE  DEVONIAN,  and 
(3)  the  LATER  or  UPPER  DEVONIAN.  The  Devonian  areas  are 
those  vertically  lined  on  the  North  American  map,  page  136. 

ROCKS. 

1.  Early  or  Lower  Devonian. —  The  Lower  Devonian  forma- 
tion has,  at  its  base,  first,  the  Oriskany  sandstone,  which  has 
most  thickness  in  eastern  New  York,  like  the  beds  of  the  Lower 
Helderberg.  Next  follows  the  Corniferous  limestone,  which  is 
the  great  limestone  of  the  Devonian,  just  as  the  Niagara  was  of 
the  Upper  Silurian,  and  the  Trenton  limestone  was  of  the 
Lower  Silurian.  It  spreads  through  New  York  from  the  Helder- 
berg Mountains  south  of  Albany,  where  it  has  been  called 
the  Upper  Helderberg  limestone,  and  stretches  on  westward 
to  the  Mississippi,  and  beyond  into  Iowa  and  Missouri. 
In  New  York  and  along  the  Appalachian  region,  it  is  under- 
laid by  a  sandstone  or  grit  rock. 

The  Corniferous  limestone  is  in  some  places  a  coral-reef 
rock,  as  plainly  as  any  coral-reef  limestone  in  modern 
tropical  seas.  At  the  Falls  of  the  Ohio,  near  Louisville, 
Kentucky,  it  consists  of  an  aggregation  of  Corals,  many  of 
large  size,  and  some  are  standing  in  the  position  of  growth. 

The  limestone  often  contains  a  kind  of  flint  called  horn- 
stone;  and,  as  the  Latin  for  horn  is  cornu,  the  limestone  was 
thence  named  the  Corniferous  limestone.  The  Devonian  de- 


172  PALEOZOIC    TIME. 

posits    above    this     limestone    are     mostly    sandstones    and 
shales. 

2.  Middle   Devonian. — The  Middle  Devonian  includes  the 
Hamilton   beds.       They   are   mainly   fragmented  deposits   in 
southern  New  York  and  along  the  Appalachian  region  to  the 
southwest;  but  in  parts  of  the  Interior  region  they  include 
limestones.     The  flagging  stone  so  much  used  in  New  York 
and  the  adjoining  states  is  an  evenly  laminated  argillaceous 
sandstone,  from  the  Hamilton  beds   at   Kingston  and  other 
places  on  the  Hudson  River. 

3.  Upper  Devonian. — The  Upper  Devonian  comprises  the 
Portage  and  Chemung  formations,  which  were  thus  named  from 
localities  in  New  York.     They  consist  chiefly  of  sandstones 
with  some  shale  in  New  York  and  Pennsylvania ;    but  in  the 
Interior   region   the   rock  is  mainly   a   black   shale   of    little 
thickness.     The  Catskill  red  sandstone  of  eastern  New  York 
and  Pennsylvania  is  a  coarse  sea-border  formation,  made  dur- 
ing the  Portage  and  Chemung  epochs. 

In  Great  Britain  the  Devonian  formation  includes  a 
great  thickness  of  red  sandstone  in  Scotland,  Wales, 
and  England,  which  was  formerly  distinguished  as  the 
"Old  Red  Sandstone."  In  South  Devon  there  are  lime- 
stone and  shales  in  place  of  red  sandstone,  and  hence  a 
greater  abundance  of  fossils.  In  the  Eifel,  Germany,  the 
Eifel  limestone  is  a  Devonian  coral-reef  rock  of  the  age 
of  the  Corniferous.  Devonian  sandstones  cover  a  large 
area  in  Russia. 


DEVONIAN   ERA. 


173 


LIFE. 

1.  Plants. — The  plants  included,  besides  Seaweeds,  various 
terrestrial  kinds;  and  among  them,  in  the  middle  and  later 
Devonian,  large  forest  trees. 

These  early  species  were  mostly  the  higher  Cryptogams  or 


FIGS.  177,  178. 


Ferns. 
Fig.  177,  Neuropteris  polymorpha;   178,  Tree-fern,  Caulopteris  antiqua. 

Flowerless  plants,  but  included  also  some  Flowering  plants. 
Of  the  former  there  were  the  following  kinds :  — 

1.  Ferns.  —  Some  of  them  were  Tree-ferns.     A  portion  of 
one   of  the   Ferns   is   shown   in   Fig.  177,   and   part  of  the 
stem  of  a  Tree-fern  in  Fig.  178. 

2.  Eqiriffeta.  —  The    modern    Equiseta,   or    Horsetails    (the 
latter  term  a  translation  of  the  former)  have  striated  jointed 
stems,  which  may  be  pulled   or  broken   apart  easily  at  the 


174 


PALEOZOIC   TIME. 


articulations.  The  ancient  species  had  a  similar  character. 
A  portion  of  one  of  these  rush-like  Devonian  plants  is  rep- 
resented in  Fig.  179.  One  of  the  articulations  of  the  stem 
is  shown  at  ab.  In  allusion  to  its  reed-like  character  it  is 
called  a  Catamites,  from  the  Latin  calamus,  a  reed.  The 
plant  represented  in  Fig.  180  belongs  to  the  Equisetum  tribe; 
the  word  Asteropliyllites  means  star-leaf. 


FIGS.  179,  180. 


Equiseta. 

Fig.  179,  Calamites  (Archoeocalainites)  radiatus ;  180,  Asterophyllites  latifolius. 

3.  Lycopods.  —  The  land  plants  most  characteristic  of  the 
world  in  ancient  time,  were  the  Lycopods.  The  little  trail- 
ing Ground  Pines  of  our  modern  woods,  so  much  used  for 
decorating  churches  at  Christmas  time,  are  examples  of 
Lycopods ;  the  close  resemblance  to  miniature  Pine  trees 
gave  origin  to  the  name.  The  earliest  of  the  ancient 
Lycopods  were  of  small  size,  but  some  of  those  of  the 
Middle  Devonian  were  large  forest  trees.  Fig.  181  repre- 
sents a  part  of  the  exterior  of  one  of  the  Devonian  Lyco- 


DEVONIAN  ERA. 


175 


pods.  The  plants  are  called  L<'/n'ii»ilc/nlri(Js  (from  the  Greek 
for  scale  and  tree),  in  allusion  to  a  resemblance  between  the 
scarred  surface  and  the  scaly  exterior  of  a  reptile.  The  scars 
are  the  bases  of  the  fallen  leaves,  and  resemble  the  same  on 
a  dried  branch  from  a  Spruce  tree.  In  the  true  Lepidoden- 
drids  the  scars  are  in  alternate  order,  as  illustrated  in 
Fig.  181.  In  another  group,  called  Sigillarids,  the  scars 
are  in  vertical  series,  as  in  Fig.  182. 

4.    Phcenogams,  or  Flowering  Plants.  —  Among  the  Flower- 


FIGS.  181-188. 


t     I 


Si 

Lycopods;  Gymnosperm. 

Figs.  181,  182,  LYCOPODS;  181,  Lei>idodendron  prim»vum ;  182,  Sigillaria  Hallii; 
Fig.  183,  GYMNOSPEBM  :  Cordaites  Robbii. 

ing  plants  there  were  trees  allied  to  the  Yew,  Spruce,  and 
Pine,  kinds  having  the  simplest  of  flowers,  and  the  seed 
naked  instead  of  in  pods.  In  allusion  to  the  latter  charac- 
ter they  are  called  Gymnosperms,  meaning  having  naked  seeds. 
The  flowers  and  fruit  are  usually  in  cone-like  groups,  and 
in  allusion  to  the  cones  a  large  part  of  Gymnosperms  are 


176 


PALEOZOIC    TIME. 


called  Conifers.  Fig.  183  is  a  leaf  of  a  Cycad,  a  subdivision 
of  the  group  of  Gynmosperins  which  includes  the  modern 
Cycas  and  Zamia. 

2.    Animals.  —  Corals,  Crinoids,  Brachiopods,  and  Trilobites, 
were  represented  by  numerous  species,  as  in  the  preceding  era. 

FIGS.  1S4-1S6. 


Polyp-Corals. 
Fig.  184,  Zaphrentis  gigantea ;  185,  Phillipsastrsea  Vcrneuili ;  186,  Favosites  Goldfussi. 

Three  of  the  Corals  of  the  coral-reef  limestone  (Corniferous 
limestone)  from  the  Falls  of  the  Ohio,  near  Louisville,  are 
represented  in  Figs.  184-186.  Fig.  184  represents  a  specimen 
of  one  of  the  large  simple  Corals,  broken  at  both  extremities, 
and  showing  above  the  radiating  plates  of  the  interior.  The 


DEVONIAN    ERA. 


177 


top,  when  perfect,  had  a  depression  Avhich  was  radiated  with 
such  plates,  and  to  this  the  name  of  this  ancient  group  of 
Corals,  Cyathophylloids,  alludes;  it  comes  from  the  Greek 
for  cup  and  leaf.  Some  specimens  of  the  species  are  nearly 
three  inches  in  diameter  at  top  and  a  foot  long;  and,  when 
living,  the  polyp  or  flower-animal  when  expanded  was  as 
large  as  a  small-sized  sunflower,  and  probably  as  brilliant  in 
color.  Fig.  185  shows  the  surface  of  a  massive  Coral  whose 
polyps  covered  the  surface  like  those  of  Fig.  14,  on  page  45. 
The  other  kind,  Fig.  186,  is  one 
of  the  most  common ;  the  struc- 
ture is  columnar,  suggesting 
that  of  a  honeycomb,  and  hence 
its  name,  Favosites,  from  the 
Latin  favus,  a  honeycomb. 

Among  Cephalopods,  besides 
species  related  to  the  Nautilus, 
or  Nautiloids,  there  were  other 
kinds  of  the  tribe  of  Ammo- 


FK,. 


Cephalopod. 
Fig.  1ST,  Goniatites  luithrax. 


nites,  or  Ammonoids,  a  group 
which  commenced  just  before 
the  close  of  the  Upper  Silurian,  and  which  is  represented  by 
very  numerous  species  in  Mesozoic  time.  The  form  of  one 
of  the  Devonian  species  is  shown  in  Fig.  187.  It  has 
the  partitions  or  septa  of  the  shell  flexed,  and  hence  the  name 
Goniatites,  from  the  Greek  for  angle.  Besides  the  flexures  on 
the  sides  shown  in  the  figure,  there  is  always  one  along  the 
DANA'S  GEOL.  STORY  — 12 


178 


PALEOZOIC   TIME. 


back  of  the  shell.  Moreover,  the  siphuncle,  instead  of  being 
central,  or  nearly  so,  as  in  the  Nautiloids,  is  close  to  the 
back  of  the  shell. 

Among  Crustaceans  there  were  Barnacles  and  Shrimps. 

FIG.  188. 


Fio.  ISfl. 


Crustacean. 

Palseopala'inon  Newberryi. 

Fig.  188  represents   the   Shrimps   from   the   Portage   beds 
of  the  Upper  Devonian. 

Besides  marine  species  there  were  also  Insects  among  ter- 
restrial Articulates.  Fig.  189 
represents  a  wing  of  one  of  the 
May-flies  of  the  Devonian  world; 
a  gigantic  species  much  exceed- 
ing any  now  known.  It  meas- 
ured five  inches  in  spread  of 
piatephemera  antiqua.  wings.  The  May-flies  or  Ephem- 

erae are  species  that  live  in  the  water  during  the  young  or 
larval  state,  and,  when  mature,  fly  in  clouds  over  moist 
places.  One  of  the  Devonian  species  could  make  the  shrill 
sound  of  a  Locust.  < 


DEVONIAN  ERA. 


179 


The  Vertebrates  included,  as  far  as  now  known,  only  Fishes. 
The  remains  of  the  Fishes  are  teeth;  large  spines  that 
formed  the  front  margin  of  the  fins;  scales;  plates  covering 
the  head  or  the  whole  body  of  armor-clad  species  or  Placo- 
derms,  but  never  the  entire  backbone  (vertebral  column),  as 

FIG.  190. 


Fin-spine  of  a  Shark. 

this  was  mainly  or  wholly  cartilaginous  and  not  bony,  and 
hence  decayed  on  burial. 

The  species  included  are  (1)  Sharks;  (2)  Gars,  or  Lepido- 
ganoids;  (3)  Placoderms;  and  (4)  Dipnoans.  The  Gars  and 
Placoderms  are  both  included  under  the  name  Ganoids. 

1.  Sharks.  —  The  remains  of  the  Sharks  are  either  the  teeth, 
che  shagreen,  or  hard,  rough-pointed  covering  of  the  body, 
or  the  large  spines  with  which  the 
front  margin  of  the  fins  is  sometimes 
armed.  Fig.  190  represents  one  of  the 
tin-spines  of  a  Shark  of  the  Corniferous 
period,  two  thirds  the  full  length.  The 
Shark  was  one  of  great  size,  as  the 
length  of  the  spine  indicates.  Some  of 
the  Sharks  had  rather  blunt  cutting  teeth;  but  the  most 
common  kind,  related  to  the  living  Cestracion  of  Australian 
seas,  had  a  pavement  of  bony  pieces  over  the  inner  surface 


FIGS.  191-193. 

192  193 


Scales  of  Ganoids. 


180 


PALEOZOIC    TIME. 


of  the  lower  jaw,   making  the  mouth  a  formidable  grinding 
apparatus,  fit  for  cracking  Brachiopods  and  the  like. 

2.  Gars,  or  Lepidoganoids. — The  Gar-pikes  of  the  Mississippi 
and  the  Great  Lakes,  now  a  rare  kind  of  Fish  in  the  world,  are 
examples  of  the  type  of  Fishes  that  was  exceedingly  abundant 

FIGS.  194-196. 
194 


Dipnoan;  Ganoids. 

Fig.  194,  DIPNOAN  :  Dipterus  macrolepidotus  (x  J) ;  Figs.  195, 196,  GAXOIDS  :  195,  Holop- 
tychius;  195  a,  scale  of  same  ;  196,  tail  of  a  modern  (homocercal)  Ganoid. 

in  species  in  the  Devonian  Age.  The  scales  of  Gars  are  bony 
and  shining,  unlike  those  of  ordinary  modern  Fishes,  and  to 
this,  Agassiz's  name,  Ganoid  (from  the  Greek  for  shining), 
refers.  In  many  species  the  scales  are  set  side  by  side  with 


DEVONIAN   ERA. 


181 


FIG.  197. 


a  special  arrangement  for  interlocking  at  one  margin  after 
the  fashion  of  the  tiles  on  a  roof;  while  in  others  they  are 
put  on  more  like  shingles,  or  in  the  way  common  in  ordinary 
fishes.  Figs.  191,  192  represent  two  kinds  of  tile-like  scales ; 
and  193,  the  under  surface  of  two  of  the  latter,  showing  how 
they  are  secured  to  one  another.  Fig.  195  represents  a  speci- 
men of  the  Ganoid  fishes  of  the  Devonian. 

Some  of  the  Ganoids  of  the  Middle  Devonian 
whose  remains  have  been  found  in  Indiana  and 
Ohio  were  of  great  size.  One  of  them  had  jaws  a 
foot  to  a  foot  and  a  half  long,  with  teeth  in  the 
lower  jaw  (Fig.  197)  two  inches  or  more  long. 

The  teeth  of  Ganoids   are   usually  very  sharp. 
Sometimes  they  are  small  and   fine,  and  grouped 
so    as   to    make    a    brush-like  surface ;    but  often 
they  are  very  large  and  stout.     The   material   of     On>-chod«8- 
the  interior  of   the  teeth,  called  dentine,  is  often  intricately 
folded,  and,  in  allusion  to  the  passages  of  a  labyrinth,  such 

teeth  are  said  to  have  within  a 
labyrinthine  structure.  A  simple 
form  of  this  labyrinthine  structure 
is  represented  in  Fig.  198. 

3.  Placoderms.  —  One  of  the  Placo- 
Section  of  Tooth  of  Lepidosteus 

osseus-  derms,  a  Cephalaspis,  is  represented 

in  Fig.  199.  Other  species  are  shown  in  Figs.  200,  201. 
The  body  in  Fig.  200  is  incased  in  bony  pieces,  and  the 
pectoral  fins  of  the  fish  were  like  arms;  but  they  made 


FIG.  198. 


182 


PALEOZOIC    TIME. 


very  poor  limbs  for  a  fish,  as  they  were  unfit  for  swimming, 
and  could  be  used  only  for  crawling  over  the  bottom. 


FIG.  199. 


Cephalaspis  Lyellii. 

4.    Dipnoans.  —  These    Fishes    resemble    the    Ganoids    in 
many   respects,  but   differ   in   having   the   air-bladder  devel- 

FIGS.  200,  201. 


200 


Placoderms. 
Fig.  200,  Pterichthys  Milled  (x  j) ;   201,  Coccosteus  decipiens  (x  \). 

oped  as  a  lung,  and  the  auricle  of  the  heart   divided  into 
two.     Fig.  194  represents  a  Devonian  Dipnoan.     The  tail  in 


DEVONIAN   ERA.  183 

Fig.  194  has  a  peculiarity  that  belonged  to  all  of  the  ancient 
Fishes  ;  that  is,  the  vertebral  column  extends  to  its  extremity. 
In  Mesozoic  and  Cenozoic  species  and  modern  Gars  the  ver- 
tebral column  stops  at  or  near  the  commencement  of  the 
tail-fin,  as  in  Fig.  196. 

The  facts  reviewed  with  reference  to  the  life  of  the 
Devonian  teach  that  during  the  progress  of  the  age  the 
marshes  and  dry  land  were  covered  with  jungles  and  forests ; 
that  the  trees  were  without  conspicuous  flowers,  and  the 
most  of  them  with  no  true  flowers  at  all;  that  the  seas 
were  brilliant  with  living  Corals,  as  well  as  Crinoids,  and 
abounded  in  Brachiopods  and  Trilobites;  that  they  also 
had  their  great  fishes,  —  Sharks,  Gars,  and  Placoderms. 
The  land,  too,  had  its  swarms  of  Insects,  and  its  Scor- 
pions and  Myriapods,  and  perhaps  also  its  Spiders  to 
spread  their  webs  for  the  May-flies,  although  no  relics  of 
them  have  yet  been  found. 

MOUNTAIN-MAKING. 

The  Devonian  age  passed  quietly  for  the  larger  part  of 
the  North  American  continent,  without  any  tilting  of  the 
rocks;  yet  not  Avithout  wide,  though  small,  changes  of 
level,  varying  the  limits  and  depth  of  the  Interior  sea, 
such  changes  of  level  and  of  limits  being  indicated  by  the 
varying  limits  of  the  rocks,  all  of  which  are  of  marine 
origin.  This  quiet  was  not  interrupted  between  the  Devo- 
nian and  Carboniferous  eras,  so  far  as  yet  discovered,  ex- 


184  PALEOZOIC   TIME. 

cept  to  the  northeast  in  the  region  of  New  Brunswick,  Nova 
Scotia,  and  northeastern  Maine.  There  an  upturning  and 
flexing  of  the  beds  occurred,  and,  as  a  result,  some  moun- 
tain-making. 

The  southward  extension  or  growth  of  the  dry  land  of  the 
continent  continued;  and,  by  the  close  of  the  Devonian,  the 
shore  line  probably  crossed  the  southern  portion  of  what  is 
now  New  York  State,  where  is  the  southern  limit  of  the 
outcropping  Devonian,  so  that  all  of  Canada  except  the  south- 
west extension  north  of  Lake  Erie,  nearly  all  of  New  York, 
and  much  the  larger  part  of  New  England,  were  above  the 
sea  level,  together  with  Wisconsin  and  the  borders  of  the  ad- 
joining states.  There  was  probably  also  a  peninsula  extending 
from  northern  Illinois  to  the  Cincinnati  region,  and  an  island 
about  an  Archaean  area  in  Missouri.  See  map,  page  !.'!<>. 

3.     Carbonic  Era,  or  Era  of  Amphibians. 

The  Carbonic  era  was  the  time  when  the  most  extensive 
coal-beds  of  America  and  Europe  were  made.  The  name 
Carbonic  is  from  the  Latin  carbo,  coal. 

ROCKS. 

1.  Subcarboniferous  Period.  —  The  era  commenced  with  a 
marine  period,  the  Subcarboniferous,  in  which  a  large 
part  of  the  North  American  continent  was  under  the  sea, 
though  not  at  great  depths,  and  Great  Britain  and  Europe  also 
were  to  a  large  extent  submerged.  During  it,  limestone  strata, 
with  some  intervening  sand-beds,  were  in  progress  in  portions 


CAEBONIC   ERA. 


185 


of  Great  Britain  and  Europe,  and  over  much  of  the  Mississippi 
basin  or  the  Interior  region  of  North  America;  and,  at  the 
same  time,  great  fragmental  deposits,  making  sandstones, 
shales,  and  conglomerates,  were  laid  down  along  the  Appa- 
lachian region  from  the  borders  of  New  York  southwestward, 
the  thickness  of  which  was  five  times  as  great  as  that  af 


the  limestone  strata. 

909 


FIGS.  202-204. 


Crinoids;  Coral. 

Figs.  202, 203,  CRINOIDS  :  202,  Woodocrinus  elegans ;  203,  Pentremites  pyriformis  ;  Fig.  204, 
CORAL  :  surface  of  Lithostrotion  Canadense. 

The  map  of  North  America  011  page  164,  Fig.  167,  gives  a 
general  idea  of  the  Continental  land  and  its  great  waters.  The 
chief  change  that  had  taken  place  during  the  Upper  Silurian 
and  Devonian  was  a  spreading  of  the  northern  shore  line  in  New 
York  far  southward  to,  or  nearly  to,  its  southern  boundary ; 
in  Ohio,  to  and  beyond  the  Cincinnati  island  (C,  Fig.  167) ; 
and  in  Wisconsin  to  northern  Illinois  and  Iowa.  Farther 
south  and  west  there  was  an  open  sea. 


186 


PALEOZOIC   TIME. 


The  limestone  was  formed  to  a  great  extent  of  Crinoids,  and 
though  Corals,  Brachiopods,  and  other  species  contributed  to  its 
material,  it  has  been  called  Crinoiilal  limestone.  The  Crinoids 
were  of  numerous  species  and  very  various  forms.  One  of  the 
most  perfect  specimens  is  represented  in  Fig.  202,  only  the 
stem  below  being  wanting.  The  figure  shows  the  numberless 
stony  pieces  —  really  blocks  of  limestone  material  —  of  which 
it  consists,  and  which  ordinarily  fell  to  pieces  when  the  ani- 
mal died,  as  there  was  little  animal  membrane  to  hold  them 
together.  The  animal  opened  out  its  arms  at  will,  and  when 


F:GS.  205,  206. 


205 


Brachiopods. 

Fig.  205,  Splrifer  increbescens  ;  206,  Productus  punctatus. 

expanded,  the  breadth  of  the  flower-like  summit  in  this  species 
was  about  three  inches.  The  stem  below,  when  entire,  was 
probably  a  foot  or  more  long.  The  little  disks  of  which  the 
stem  of  the  Crinoid  consists,  looking  like  button-molds,  are 
common  fossils  in  the  limestones.  On  page  50,  Fig.  34,  a 
piece  of  Crinoidal  limestone  is  represented  which  consists 
almost  solely  of  the  broken  stems  of  Crinoids.  Some  of 


CARBONIC    ERA.  187 

the  stems  are  an  inch  in  diameter.  Pig.  203  represents  a 
Crinoid  without  arms,  called  Pentremites. 

There  were  also  Corals ;  and  a  top  view  of  the  most  com- 
mon of  these  is  represented  in  Fig.  204.  Brachiopods  also 
were  abundant ;  figures  of  two  of  them  are  given  in  Figs. 
205,  206. 

2.  Carboniferous  Period. — After  the  Subcarboniferous  pe- 
riod began  the  true  Coal  period,  or  that  of  the  coal-measures. 

The  rocks  of  the  coal-measures,  which  alternate  with  the 
coal-beds,  are  sandstones,  shales,  conglomerates,  and  occasion- 
ally, especially  in  the  Interior  region  of  the  continent,  lime- 
stones. At  base,  there  is  generally  a  conglomerate  called  the 
millstone-grit.  The  coal-beds  are  evidence  of  long  periods  of 
emerged  land,  free  from  briny  waters,  where  marshy  lands 
were  densely  covered  with  vegetation ;  and  the  intervening 
fragmental  and  limestone  strata  prove  a  new  submergence 
either  beneath  fresh  waters  or  salt,  and  generally  for  the 
region  west  of  Pennsylvania,  the  latter,  as  the  fossils  show. 

The  geography  of  the  continent  during  times  of  emergence 
and  wide-spread  foliage  may  be  learned  approximately  from 
the  map  on  page  136  (since  at  those  times  the  Archaean  and 
Paleozoic  areas  must  have  been  mainly  dry  land) ;  and  the 
positions  of  the  great  coal-marshes,  though  narrowed  by 
erosion  and  a  covering  of  later  strata,  from  the  black  areas 
on  the  map.  The  easternmost  is  in  New  Brunswick,  Nova 
Scotia,  and  western  Newfoundland;  the  westernmost,  just 
west  of  the  Mississippi,  from  Iowa  to  Texas ;  the  region 


188  PALEOZOIC   TIME. 

farther  west  continued  to  be  an  area  of  salt  water,  producing 
only  marine  Carboniferous  rocks. 

The  most  northern  area,  the  Acadian,  covers  part  of  New- 
foundland, Nova  Scotia,  and  New  Brunswick ;  a  second,  of 
very  small  extent,  is  in  Rhode  Island ;  a  third,  the  Alleyliany, 
reaches  from  near  the  southern  boundary  of  New  York  over 
part  of  Pennsylvania,  Ohio,  Kentucky,  and  Tennessee  to 
Alabama ;  a  fourth  is  in  central  Michigan  ;  a  fifth,  the  Eastern 
Interior,  covers  parts  of  Illinois,  Indiana,  and  west  Kentucky ; 
a  sixth,  the  Western  Interior,  parts  of  Iowa,  Missouri,  Kansas, 
Arkansas,  and  Texas.  The  last  two  were  originally  one,  but 
the  Mississippi  Valley  now  separates  them.  It  has  been 
estimated  that  the  area  of  the  workable  coal-beds  of  the 
United  States  is  at  least  120,000  square  miles.  The  coal  area 
of  Nova  Scotia  and  New  Brunswick  is  18,000  square  miles. 

The  principal  coal  areas  of  England  are  those  of  South 
Wales ;  the  great  Lancashire  region  east  of  Liverpool  (B, 
Fig.  230,  p.  212)  and  Manchester  (C) ;  the  Derbyshire 
coal  region  farther  east ;  and  on  the  northeastern  coast,  the 
Newcastle  coal-field  (D).  There  are  also  coal-fields  in  Scot- 
land between  the  Grampian  range  on  the  north  and  the  Lam- 
mermoor  Hills  on  the  south ;  and  others,  in  Ulster,  Connaught, 
Leinster  (Kilkenny),  and  Minister,  in  Ireland.  There  are 
valuable  coal-fields  of  smaller  extent  in  Belgium,  France,  and 
Spain,  and  others  in  Germany  and  southern  Eussia. 

The  greatest  thickness  of  the  coal-measures  in  Pennsyl- 
vania is  4000  feet 5  in  Illinois,  1200  feet;  in  Nova  Scotia, 


CARBONIC   ERA.  189 

about  15,000  feet.  In  Great  Britain  it  is  7000  to  12,000  feet 
in  South  Wales,  and  contains  100  beds  of  coal;  7000  to 
8000  feet  in  Lancashire,  with  40  beds  of  coal  over  one 
foot  in  thickness ;  2000  feet  at  Newcastle,  with  about  60 
beds  of  coal.  The  aggregate  thickness  of  the  coal-beds  of  a 
region  is  not  over  one  fiftieth  of  that  of  the  coal-measures. 

The  coal-beds  vary  in  thickness  from  less  than  an  inch  to 
30  or  40  feet.  The  "mammoth  vein"  of  the  anthracite 
region  in  Pennsylvania  is  29  feet  thick  at  Wilkesbarre;  but 
there  are  some  layers  of  shale  in  the  course  of  it,  —  a 
common,  fact  in  all  coal-beds.  Some  coal-beds  contain  too 
much  earthy  matter  to  be  of  any  value. 

The  mineral  coal  is  of  different  kinds.  That  of  eastern 
Pennsylvania  and  of  Khode  Island  is  anthracite,  while  that 
of  the  rest  of  the  country  is  almost  wholly  bituminous  coal. 
Anthracite  is  a  firm,  lustrous  coal,  burning  with  but  little 
flame,  while  the  bituminous  coal,  as  that  from  Pittsburg  and 
the  states  west,  is  less  firm  and  usually  of  less  luster,  and 
burns  with  much  yellow  flame.  The  flame  is  due  mainly  to 
the  fact  that  part  of  the  carbon  is  combined  with  hydrogen 
(or  with  hydrogen  and  oxygen)  into  a  compound  that,  when 
heat  is  applied,  becomes  a  combustible  gas.  Some  bituminous 
coals  —  especially  those  compact  coals,  scarcely  shining,  called 
cannel  coal  —  afford  50  per  cent  or  more  of  volatile  matter; 
while  anthracite  yields  very  little,  and  this  is  mostly  the 
vapor  of  water. 

Coals  always  contain  some  impurity,  which  is  the  "ash" 


190  PALEOZOIC   TIME. 

and  "  clinkers  "  of  a  coal-fire.  This  ash  or  earthy  material 
was  largely  derived  from  the  plants  themselves,  and  for 
the  best  coals  wholly  so;  but  in  other  cases  it  is  part  of 
the  detritus  that  was  from  time  to  time  drifted  over  the 
beds  of  vegetable  debris  by  the  winds,  or  washed  over  by 
the  waters.  The  coal-beds  always  contain  a  little  sulphur,— 
enough  to  give  a  sulphur  smell  to  the  gases  from  the  burn- 
ing coal;  and  the  most  of  it  exists  in  the  state  of  pyrite,  a 
compound  of  iron  and  sulphur. 

The  layer  of  rock  under  a  coal-bed  is  often  a  clayey 
layer,  called  the  underclay,  and  it  is  frequently  full  of  the 
underground  stems  or  roots  of  plants.  The  trunks  sometimes 
project  from  the  top  of  a  bed  of  coal,  as  shown  in  Fig.  86, 
page  109.  Many  logs  or  great  trunks  lie  in  the  strata  that 
intervene  between  the  coal-beds,  which  were  once  floating 
logs;  and  multitudes  of  ferns  and  flattened  stems  or  trunks 
of  these  and  other  plants  are  often  spread  out  in  the  shales, 
and  especially  in  the  bed  of  rock  directly  over  a  coal-bed. 
Moreover,  the  coal  itself,  even  the  hardest  anthracite,  has 
sometimes  impressions  of  plants  in  it,  and,  more  than  this, 
contains  throughout  its  mass  vegetable  fibers  in  a  coaly 
state  which  the  microscope  can  detect. 

Coal  was  made  from  plants,  and  each  coal-bed  was  origi- 
nally a  bed  of  vegetable  material,  accumulated  in  nearly  the 
same  way  as  the  peat-beds  of  the  present  time.  (See,  on 
this  point,  page  57.)  The  plant-bed  having  increased  until 
several  times  thicker  than  the  coal-bed  to  be  made  out  of 


CARBONIC   ERA.  191 

it,  was  finally  covered  with  beds  of  clay  or  sand;  and  while 
thus  buried  it  gradually  changed  to  coal. 

Plants  when  dried  are  one  half  carbon  —  the  chief  ma- 
terial of  charcoal  —  the  rest  being  mostly  the  two  gases, 
oxygen  and  hydrogen;  after  the  change  to  coal,  seven  tenths 
to  nine  tenths  or  more  of  the  whole  is  carbon. 

3.  Permian  Period.  —  The  coal-measures  are  followed .  in 
Europe  by  a  series  of  red  sandstones  and  clayey  rocks  or 
marlytes,  with  a  magnesiaii  limestone,  constituting  the  Per- 
mian group —  so  called  from  the  district  of  Perm,  in  Russia. 
In  North  America  the  Permian  rdcks  include  the  sandstones 
and  shales  at  the  top  of  the  coal-measures  in  Kansas,  Penn- 
sylvania, and  Texas. 

LIFE. 

1.  Plants.  —  The  plants  were  similar  in  general  character 
to  their  predecessors  in  the  Devonian  age,  though  mostly 
different  in  species  and  partly  in  genera.  Of  the  higher 
Cryptogams,  called  Acrogens  (or  upward  growers,  as  the 
word  from  the  Greek  signifies),  because  they  can  grow  into 
trees,  there  were,  as  in  the  Devonian,  (1)  Ferns,  (2)  Equiseta, 
(3)  Lycopods;  and  of  the  Phsenogams,  or  flowering  plants, 
Gymnosperms,  or  trees  of  the  Pine  and  Cycad  tribes.  The 
trees  and  shrubs  grew  luxuriantly  over  the  almost  endless 
marshes  of  the  continent,  and  spread  beyond  them,  also, 
over  the  higher  lands. 

The  features  of  the  vegetation  and  of  the  ordinary  land- 
scape are  shown  in  the  following  ideal  sketch,  Fig.  207. 


192 


PALEOZOIC  TIME. 


The  tree  at  the  center  is  a  Tree-fern,  and  there  are  smaller 
Ferns  below.  The  tree  near  the  left  side  is  a  Lycopod  of 
the  ancient  tribe  of  Lepidodendrids ;  in  the  left  corner  there 


PIG.  207. 


Carboniferous  Vegetation. 


are  Equiseta.  The  region  is  represented  as  a  great  marshy 
plain  with  lakes.  The  lakes  of  the  Carboniferous  era  probably 
had  their  many  floating  islands  of  vegetation,  carrying  large 
groves  like  the  floating  islands  of  some  lakes  iu  India. 


CARBONIC   EKA. 


193 


A  portion  of  one  of  the  Ferns  is  shown  in  Fig.  208,  and 
of  another  in  Fig.  209.  Fig.  210  represents  one  of  the 
Equiseta,  a  species  of  Calamites  (page  174);  plants  with 
jointed  stems  that  grew  often  to  a  height  of  20  feet,  and 

Fiu.  208. 


w«* 


Fern. 
Sphcnopteris  Gravcnhorstii. 


sometimes    were    a   foot  in    diameter,  very  unlike  the  little 
Horsetails  of   modern  time. 


Fir;.  209. 


Wwlm^ 

Fern. 

Neuropteris  hirsuta. 

The   Lycopods,  of   the   tribe  of   Lepidodendrids,   had   the 

aspect   of    Pines  and   Spruces,  and   were   40   to  80   feet  or 

more  in  height.     On  some,  the  slender  pine-like  leaves  were 
DANA'S  GEOL.  STORY  — 13 


194 


PALEOZOIC    TIME. 


a  foot  or  more  long.      Figs.  211,  212  show  the  scars  of  the 
outer   surface   of    two   of    the   Lepidodendrids    arranged,   as 


FIG.  210. 


Equisetum. 
Calamites  canna'formis. 

usual,  in  alternate  order ;  and  Fig.  213,  those  of  a  Sigillaria 
in  vertical  series.      The  resemblance  of  the  scars  in  the  latter 

FIGS.  211-213. 
212 


213 


W 

• 

it 

3 

V. 

W 

/ 

9 

L 

Lycopods. 
Fig.  211,  Lepidodendron  clypeatum  ;   212,  Halonia  imlchella;   213,  Sijrillnria  Sillimani. 


to   an   impression  of  a   seal   suggested  the  name  SigiUarin, 
from  the  Latin  sigillum,  seal. 

The    cones    of    the   Lepidodendrids   and   the   nuts   of    the 


CARBONIC   ERA. 


195 


FIGS.  214,  215. 
214  215 


Gymnosperms  also  occur  in  the  beds.  Two  of  these  nuts 
are  represented  in  Figs.  214,  215.  They  are  supposed  to 
have  belonged  to  trees  related  to  the  modern  Yew  tree. 

Many  of  the  North  American 
species  of  plants  have  been  found 
also  in  Europe.  There  are  also 
coal  regions  in  the  Arctic  islands 
which  have  afforded  some  of  the 
same  species  of  plants  that  were 
growing  in  Europe  and  America, 
showing  great  uniformity  in  the 
climate  of  the  era;  a  fact  sus- 
tained also  by  the  occurrence  in 
the  Arctic  deposits  of  many  fos- 
sil shells  and  corals  identical 
with  some  then  living  in  the  seas  of  Europe  and  America. 

2.  Animals.  —  The  seas  of  the  Carboniferous  age  abounded 
in  Crinoids,  Corals,  and  Brachiopods ;  but  in  the  group 
of  Articulates,  while  there  were  many  kinds  of  Worms  and 
Crustaceans,  Trilobites  were  few.  Trilobites  had  been  re- 
placed by  other  Crustaceans.  Examples  of  the  Crinoids, 
Corals,  and  Brachiopods  of  the  earlier  part  of  the  era  are 
figured  on  pages  185,  186. 

The  land  had  its  Insects,  true  Spiders,  Scorpions,  and  Myr- 
iapods,  and  also  its  land  Snails ;  and  among  the  Insects  there 
were  May-flies,  Cockroaches,  Crickets,  and  Beetles.  A  view  of 
one  of  the  May-flies,  of  natural  size,  is  shown  in  Fig.  216 ;  of 


Nuts  of  Gymnospenns. 
Fig.   214,    Trigonocarpus    tricuspida- 
tus;  215,  T.  ornatus  ;  215  a,  view 
of  lower  end  of  same. 


196 


PALEOZOIC   TIME. 


the  wing  of  a  Cockroach,  in  Fig.  217  ;  of  a  Spider,  from  Morris, 
Illinois,  in  Fig.  218 ;  and  of  a  Myriapod,  from  Nova  Scotia,  in 
Fig.  219. 

Fishes  were  in  great  numbers  and  of  large  size,  and  they 
belonged  mostly  to  the  two  grand  divisions  that  were  espe- 

Fios.  216-219. 


Terrestrial  Articulates. 

Figs.  216,217,  INSECTS:  216,  Miamia  Bronsoni  (x  1);  217,  Eoblattina  venusta,  wing  of  a 
Cockroach ;  Fig.  218,  SPIDER  :  Arthrolycosa  antiqua ;  Fig.  219,  CENTIPEDE  :  Xylobius 
sigillariae. 


cially  characteristic  of  the  Devonian,  —  the  /Sharks  (called 
also  Selachians,  from  the  Greek  for  cartilage,  the  Sharks 
being  fishes  with  a  cartilaginous  skeleton)  and  the  Ganoiila. 
Some  of  the  Sharks  were  larger  than  any  modern  species. 
One  of  the  Ganoids  of  the  coal-measures  is  represented  in 


CARBONIC   ERA.  197 

Fig.  220.  It  has  the  vertebrated  tail,  characteristic  of  all 
Paleozoic  fishes.  Fig.  221  shows  the  form  and  size  of  the 
teeth  of  one  of  the  Sharks  of  the  Subcarboniforous  beds  of 
Illinois. 

Besides  Fishes  there  were  the  first  of  terrestrial  Vertebrates, 
Amphibians;  and,  before  the  close  of  the  Permian,  Reptiles. 
Footprints  of  an  Amphibian  have  been  described  from  the 

FIGS.  220,  221. 
220 


Fishes. 

Fig.  220,  GANOID:  Eurylepis  tuberculatus,  from   the  coal-formation  in  Ohio;  Fig.  221, 
SELACHIAN  :  tooth  of  Carcharopsis  Wortheni ;  a,  profile  section  of  same. 

Subcarboniferons  beds  of  Pennsylvania,  indicating  a  large 
animal  having  a  tail,  —  the  tail  having  made  its  mark  on  the 
mud-flat  over  which  the  animal  marched.  In  the  Carbonif- 
erous beds  of  Illinois,  Ohio,  and  Nova  Scotia,  skeletons  have 
been  found.  One  of  them,  from  Ohio,  is  represented  in  Fig. 
222.  It  has  the  broad  cranium  that  is  found  in  the  Frog 
and  Salamander ;  but  while  modern  species  have  a  naked 
skin,  the  Carboniferous  kinds  were  furnished  with  scales 
and  bony  plates.  They  had  also  sharp  teeth  very  much 
like  those  of  Ganoid  fishes. 

Fig.   223    represents   the  skull  of  one  of  the  true  Reptiles 
from  the  Middle  Permian  of  Saxony. 


198 


PALEOZOIC    TIME. 


No  remains  of  Birds  or  of  Mammals  have  yet  been  found  in 
any  Paleozoic  rocks. 

CHANGES    OF   LEVEL    DURING   THE   PROGRESS    OF    THE    CAR- 
BONIC  ERA. 

Changes   of  level  were  going  on  over  the  North  American 
FIG.  222.  continent  throughout  the 

era ;  but  they  were  alter- 
nating oscillations  above 
and  below  the  sea  level 
and  of  the  gentlest  and 
slowest  kind  possible,  not 
upliftings  into  mountains. 
Just  such  alternations  of 
level  had  been  in  progress 
through  all  the  preceding 
ages  ;  but  the  Carbonifer- 
ous movements  were  pe- 
culiar in  this,  that  the 
continent  over  its  broad 
surface  was  just  balancing 
itself  near  the  water's  sur- 
face, part  of  the  time 
bathing  in  it,  and  then 
out  in  the  free  air,  and  so  on,  alternately ;  while  in  for- 
mer times,  the  oscillations  seldom  carried  the  Interior 
Continental  region  out  of  the  water,  or  if  they  did,  only 
portions  at  a  time.  It  was  peculiar  also  in  the  fact  that 


, 

Amphibian . 
Pelion  Lyellii. 


CARBONIC    ERA.  199 

the  wide  continent  lay  quiet  above  the  sea  level,  with  a 
nearly  even  surface,  for  very  great  periods  of  time,  —  suf- 
ficiently long  to  make  beds  of  vegetable  debris  thick  enough 
for  coal-beds.  Many  of  the  coal-beds  are  six  feet  thick,  and 
some  twenty  or  more  ;  and  even  six  feet  would  require,  accord- 
ing to  an  estimate  that  has  been  made,  a  bed  of  vegetable 
debris  thirty  feet  thick  for  bituminous  coal,  and  a  much 
thicker  one  for  anthracite. 

FIG.  223. 


Reptile. 

Skull  of  Pala'ohatteria  longicaudata. 

The  Interior  of  the  continent  from  eastern  Pennsylvania 
to  central  Kansas  was  a  region  of  vast  jungles,  lakes  with 
floating  grove-islands,  and  some  dry-land  forests,  and  the 
debris  of  the  luxuriant  vegetation  produced  the  accumulating 
plant-beds.  A  Cincinnati  area  of  emerged  land  then  divided 
the  continental  marsh  from  northern  Illinois  southeastward 


200  PALEOZOIC   TIME. 

through  Kentucky ;  but  farther  south  the  eastern  and  western 
portions  were  probably  united.  The  Michigan  coal  area  was  an 
independent  marsh  region.  The  Green  Mountains  separated 
the  Pennsylvania  area  from  those  of  Rhode  Island  and  Nova 
Scotia.  The  two  latter  were  probably  connected  along  the 
region  of  the  Bay  of  Fundy  and  Massachusetts  Bay  and 
also  with  the  coal  area  of  western  Newfoundland. 

The  changes  of  level  could  hardly  have  carried  up 
evenly  all  parts  of  the  Interior  marsh  region  from  Penn- 
sylvania to  beyond  the  Mississippi ;  and  it  is  evident  that 
they  did  not,  since  it  is  difficult  to  make  out  the  parallel- 
ism between  the  beds  of  the  eastern,  central,  and  western 
portions. 

The  era  of  verdure  during  which  a  plant-bed  was  in 
progress  finally  came  to  its  end  by  a  return  of  the  water 
over  the  Continental  Interior  destroying  the  terrestrial  life ; 
and  then  began  the  deposition  of  sediment  (covering  up  the 
plant-beds  and  making  sandstones  or  shales  or  conglom- 
erates), or  the  forming  of  limestones.  Over  Illinois  and  to 
the  south  and  west,  the  encroaching  waters  were  salt;  for 
the  beds  contain  marine  fossils.  But  over  Pennsylvania 
they  were  most  of  the  time  fresh. 

Finally,  the  continental  surface,  or  wide  portions  of  it,  again 
emerged  slowly,  putting  an  end  to  aquatic  life,  and  opening  a 
new  era  of  verdure.  Such  alternations  continued  until  all  the 
successive  coal-beds  were  made,  some  of  them  affecting  per- 
haps the  whole  breadth  of  the  Interior  coal  area,  others 


GEOGRAPHICAL  PROGRESS.  201 

more  local.  Thus  the  era  was  one  of  constant  change ;  yet 
change  so  gradual  that  only  a  being  whose  years  were 
thousands  or  tens  of  thousands  of  our  years  would  have 
been  able  to  discover  that  any  change  was  in  progress. 

In  Nova  Scotia  the  oscillations  went  on  until  nearly  15,000 
feet  of  deposits  were  formed ;  and  in  that  space  there  are 
76  coal-seams  and  dirt-beds ;  and  therefore  76  levels  of 
marshes  and  verdant  fields,  between  others  when  the  waters 
covered  the  land.  But  over  that  region  the  waters  sub- 
merging the  region  were  mainly  fresh  or  brackish  waters, 
since  no  marine  shells  exist  in  the  beds,  while  there  are 
land  and  fresh-water  shells  and  bones  of  amphibians.  The 
area  in  the  Carboniferous  period  was  an  immense  delta  at 
the  mouth  of  the  St.  Lawrence,  then  the  only  great  river 
of  the  continent,  and  the  submergences  were  connected  with 
the  floods  of  the  stream  as  well  as  with  changes  of  level  in 
the  earth's  crust. 

The  Permian  period,  or  the  closing  part  of  the  Carbonifer- 
ous age,  was  an  era  of  general  submergence,  without  long 
eras  of  verdure  or  the  formation  of  plant-beds. 

GEOGRAPHICAL  PROGRESS  DURING  PALEOZOIC  TIME. 

In  the  history  of  Archaean  time  the  fact  is  brought  out 
that  the  North  American  continent  was  largely  outlined  and 
the  courses  of  its  mountain  chains  determined  before  Paleo- 
zoic time  began.  Later  history  has  shown  that  the  continent- 


202  PALEOZOIC   TIME. 

making  which  followed  was  not  a  building  up  from  deep-sea 
foundations,  but  a  building  outward  over  shallow  Continental 
seas  from  the  borders  of  the  emerged  Archaean  lands,  and 
largely  within  waters  that  had  Archaean  ridges  as  confines. 
Through  the  Early  Paleozoic,  rock-making  reached  to  the 
borders  of  the  Continental  areas.  But  at  the  time  of  the 
Medio-Paleozoic  upturning,  when  the  Taconic  Mountain  sys- 
tem was  made  (see  map,  page  164),  a  broad  sea-border  bar- 
rier was  produced  by  *an  emergence  which  shut  off  the 
Atlantic.  Consequently,  no  rock  deposits  were  made  during 
the  Later  Paleozoic  along  this  border  north  of  Florida, 

except  in  local  gulfs  over  New  England  and  Canada.     Eock- 

• 

making  in  eastern  North  America  was  largely  Interior  Conti- 
nental work.  It  produced  a  gradual  extension  of  the  founda- 
tion rocks  westward,  and  finally  their  partial  emergence. 

Over  the  Eocky  Mountain  slopes  also  there  was  rock-making ; 
but  the  larger  part  of  western  North  America,  even  to  the 
Pacific,  continued  to  the  end  of  Paleozoic  time  a  wide  sea. 

The  Post-Paleozoic  Revolution. 

From  the  beginning  of  Paleozoic  time  to  its  close  all 
changes  over  the  Appalachian  region  west  of  the  Archaean 
ridges,  southwest  of  New  England,  and  over  the  great  Inte- 
rior region  of  the  continent,  had  gone  on  quietly.  There 
were  gentle  oscillations  of  the  surface  and  slight  displace- 
ments, but  nowhere  a  general  upturning. 

These    ages   of   quiet   and   regular    work    in    rock-making 


POST-PALEOZOIC    REVOLUTION.  203 

were  very  long,  for  Paleozoic  time  includes  at  least  three 
fourths  of  all  time  after  the  beginning  of  the  Cambrian  era. 

Over  the  Appalachian  region  from  New  York  southward, 
the  Cambrian,  Silurian,  Devonian,  and  Carboniferous  deposits 
have  great  thickness.  The  maximum  amount  in  Pennsylvania 
has  been,  estimated  at  40,000  feet,  or  over  seven  miles.  But 
over  the  Interior  region,  where  limestones  were  the  most  of 
the  time  forming,  the  thickness  is  from  3000  to  4000  feet. 
These  Appalachian  deposits,  ten  times  thicker  than  those  of 
the  Interior,  were  accumulating  there  for  the  making  of  a 
range  of  mountains;  and  at  the  close  of  the  Paleozoic  all 
was  ready  and  the  mountains  were  made. 

An  account  of  the  making  of  the  Appalachian  range  has  been 
given  on  pages  114, 115.  It  is  there  stated  that  the  40,000  feet 
of  deposits  were  accumulated  in  a  gradually  forming  trough 
made  by  the  slow  sinking  of  the  earth's  crust,  the  several  rocks 
of  the  series  bearing  evidence  that  they  were  made  in  shallow 
waters.  The  last  in  the  series,  the  Carboniferous  and  Permian 
beds,  were  spread  out  horizontally  just  above  or  just  below  the 
surface ;  the  coal-measures  proving  that  there  were  wide  emer- 
gences during  their  progress.  The  amount  of  subsidence,  there- 
fore, was  in  some  places  40,000  feet.  The  breadth  of  the  trough 
was  nearly  100  miles  and  its  length  about  900. 

The  catastrophe  consisted  in  (1)  the  folding,  (2)  the  fractur- 
ing, (3)  the  solidifying,  and  in  part  (4)  the  crystallizing  of 
the  beds;  and  also  (5)  the  change,  in  eastern  Pennsylvania, 
of  bituminous  coal  to  anthracite. 


204 


PALEOZOIC   TIME. 


The  folds  were  numerous,  and  involved  the  whole  breadth 
of  the  region;  and  if  their  tops  had  not  since  been  worn  off 
by  the  action  of  water,  some  of  the  folds  would  now  rise 
over  10,000  feet  above  the  sea  level.  Their  characters  are 
shown  in  Fig.  224,  of  a  section  from  Virginia,  extending 


FIG.  224. 


VI     A/VIYIV     HI     IT" 

Section  from  the  Great  North,  to,the  Little  North,  Mountain,  through  Bore  Springs, 

Virginia. 

from  the   southeast   on   the   right   to   the   northwest   on   the 
left,  over  a  distance  of   six  miles.      It  presents  an  example, 

FIGS.  225,  226. 

..•••''""  •••"'-•',••"'' 

225 


Sections  of  the  Coal-measures. 

Fig.  225,  on  the  Schuylkill,  Pa.  ;  P,  Pottsville  on  the  Coal-measures  ;  14,  the  Coal-measures  ; 
13,  Subcarboniferous ;  12-8,  Devonian  formations ;  7,  5,  Upper  Silurian  ;  4,  3,  Lower 
Silurian  ;  2,  Cambrian.  Fig.  226,  Anthracite  region,  near  Nesquehoning,  Pa. ;  the  black 
lines  coal-beds. 

as  explained  on  page  110,  of  the  denudation  the  country  has 
undergone,  as  well  as  of  the  folding. 

The  coal-formation  was  involved  in  the  folds,  a  fact 
which  proves  that  the  folding  began  after  the  coal-beds 
were  formed.  Fig.  225  is  a  section  of  the  vicinity  of  Potts- 


POST-PALEOZOIC   REVOLUTION.  205 

ville,  Pennsylvania,  P  being  the  position  of  Pottsville 
on  the  coal-measures.  Fig.  226  represents  another  from 
near  Nesquelioning,  Pennsylvania,  showing  the  anthracite 
beds  doubled  up,  and  in  part  vertical. 

The  folds  are  steepest  and  most  numerous  to  the  south- 
eastward, or  toward  the  ocean,  and  diminish  to  the  north- 
westward (see  Fig.  224). 

The  folds  generally  have  the  western  slope  steepest,  as 
if  pressure  from  the  direction  of  "the  ocean  had  pushed 
them  westward ;  and  sometimes  the  tops  have  thus  been 
made  to  overhang  the  western  base  (Fig.  225). 


Section  of  the  Paleozoic  Formations  of  the  Appalachians,  in  Southern  Virginia, 

between  Walkers  Mountain  and  the  Peak  Hills  (near  Peak  Creek  Valley.) 

F,  fault ;  n,  Lower  Silurian  limestone ;  b,  Upper  Silurian  ;  c,  Devonian ;  d,  Subcarbon- 

iferous,  with  coal-beds. 

The  rocks  were  also  fractured  on  a  grand  scale,  and 
those  of  the  eastern  side  of  the  fracture  shoved  up  so  as  to 
make  faults  in  some  cases  of  more  than  10,000  feet.  Fig. 
227  represents  one  of  these  great  faults.  The  fault  is  at  F; 
to  the  right  of  F,  at  d,  is  the  Subcarboiiiferous,  and  to  the 
left,  a  bent-up  Lower  Silurian  limestone;  so  that  a  Lower 
Silurian  rock  is  brought  up  to  a  level  with  the  Subcarbon- 
iferous,  a  lift,  according  to  Lesley,  of  20,000  feet. 


206  PALEOZOIC   TIME. 

The  rocks  were  solidified  through  the  aid  of  the  heat 
caused  by  the  movement  of  the  rocks;  and  by  the  same 
means  the  change  of  the  coal  to  anthracite  was  caused. 
This  change  to  anthracite  took  place  where  the  rocks  are  xip- 
turned  or  disturbed,  and  therefore  where  more  or  less  heat 
had  been  produced  by  the  movements. 

While  there  was  so  much  folding  and  fracturing,  there 
was  no  chaotic  confusion  of  the  rocks  produced,  the  stratifi- 
cation being  perfectly  retained. 

It  follows  from  the  facts  (1)  that  the  force  acted  quietly, 
or  with  extreme  slowness,  for  otherwise  confusion  would 
have  been  produced ;  and  (2)  that  the  pressure  acted  from  the 
direction  of  the  ocean,  the  forms  of  the  folds,  and  their 
great  numbers  and  steepness  in  that  direction,  proving  this. 

On  page  115  all  this  folding,  faulting,  and  uplifting  is  at- 
tributed to  lateral  pressure  caused  by  the  earth's  slow  con- 
traction from  cooling. 

Owing  to  this  pressure,  and  the  weakening  of  the  bottom 
of  the  great  trough  or  syncline  by  the  high  heat  of  the 
earth's  interior,  there  was  a  yielding  below  and  a  collapse, 
and  thereby  a  pressing  together  of  the  thick  deposits, 
folding  and  breaking  them;  and  also  a  raising  of  the  upper 
surface  above  its  previous  level,  because  the  width  of  the 
base  on  which  they  rested  was  narrowed  by  the  collapse. 

Besides  an  Appalachian  range,  there  was  made  at  this 
time  in  eastern  North  America  a  Nova  Scotia  range  from 
Newfoundland  to  Rhode  Island,  since  largely  denuded;  and 


POST-PALEOZOIC    REVOLUTION. 


207 


in   Arkansas   a   Ouacliita    range.     The    three    constitute    the 
Appalachian  Mountain  system. 

The  end  of  Paleozoic  time  was  thus  marked  by  the  making 
of  great  mountain  ranges.  Beyond  this  there  was  the  emer- 
gence of  the  eastern  half  of  North  America,  leaving  the  western 
half  under  water  for  completion  and  emergence  at  the  close 

FIG.  228. 


Map  of  North  America  after  the  Post-Paleozoic  Revolution. 

of  Mesozoic  time,  as   exhibited   on   the   accompanying  map, 
Fig.  228. 

Mountains  were  made  in  Europe  and  Great  Britain  at  the 
same  time  with  those  of  the  Appalachian  Mountain  system,  so 
that  the  close  of  Paleozoic  time  has  its  mountain  boundary 
elsewhere  besides  in  America. 


208  PALEOZOIC   TIME. 

CHANGES  IN  PALEOZOIC  LIFE  AT  THE  CLOSE  OF  THE  ERA. 

In  Paleozoic  time  Crinoicls,  Brachiopods,  Cyathophylloid 
Corals,  Orthocerata,  Trilobites,  vertebrate-tailed  Ganoid  Fishes, 
among  animals,  and  Lepidodendrids,  Sigillarids,  and  Calamites, 
among  plants,  were  characteristic  species  in  each  of  the  classes 
to  which  they  belong.  With  the  close  of  it,  Trilobites,  Lepi- 
dodendrids, and  Sigillarids  became  extinct ;  Cyathophylloid 
Corals,  Orthocerata,  and  vertebrate-tailed  Ganoids  nearly  so; 
and,  afterward,  Brachiopods  among  Molluscoids,  and  Crinoids 
among  Radiates,  were  greatly  inferior  in  numbers  and  impor- 
tance to  other  types  of  more  modern  character.  It  is  thus 
that  the  Paleozoic  features  of  the  world  passed  by. 

The  characteristics  of  the  following  age,  the  Mesozoic,  had 
in  part  appeared  before  the  Paleozoic  ended ;  for  Shrimps  and 
perhaps  Crabs,  the  highest  of  Crustaceans,  had  appeared,  and 
Ammonoids  among  Mollusks;  and  Spiders  and  Insects,  some 
of  the  latter  even  emulating  large  Birds  in  size,  they  having 
a  spread  of  wing  of  two  or  three  feet.  There  were  also,  along 
the  water  margins,  Amphibians  and  the  earliest  of  Reptiles, 
as  precursors  of  Mesozoic  life.  Moreover,  among  plants, 
Cycads,  which  had  their  maximum  display  in  Mesozoic  time, 
were  well  represented  by  their  earliest  species  in  the  later 
Paleozoic. 

The  extinction  of  species  at  the  close  of  the  Paleozoic  was 
so  nearly  universal  that,  thus  far,  no  species  of  the  Permian 
period  have  been  found  in  rocks  of  later  date.  But  the  rocks 


REPTILIAN    ERA.  209 

now  in  view  were  those  that  were  made  over  the  Continental 
seas,  and,  more  correctly,  over  only  portions  of  those  seas ; 
and  hence  they  give  no  facts  as  to  the  species  of  the  ocean, 
but  an  imperfect  record  of  those  of  the  Continental  seas. 

III.     MESOZOIC  TIME. 

MESOZOIC  TIME,  or  the  Keptilian  era,  is  divided  into  three 
periods:  (1)  the  TRIASSIC,  named  from  the  Latin  tria,  three, 
in  allusion  to  the  fact  that  the  rocks  in  Germany  have  three 
subdivisions;  (2)  the  JURASSIC,  named  after  the  Jura  Moun- 
tains between  France  and  Switzerland,  (3)  the  CRETACEOUS, 
named  from  the  Latin  creta.  chalk,  the  formation  including  the 
chalk-beds  of  England  and  Europe. 

The  Mesozoic  areas,  on  the  map,  page  136,  are  lined  obliquely 
from  the  left  above  to  the  right  below. 

1.     Triaash'  <in<I  Jm-axtsic  Periods. 

BOCKS. 

* 

These  Triassic  rocks  on  the  Atlantic  border  occupy  long,  nar- 
row areas,  parallel  with  the  Appalachian  chain,  from  the  Gulf 
of  St.  Lawrence  southwestward.  One  of  them  lies  along  the  east 
side  of  the  Bay  of  Fundy ;  another,  in  the  Connecticut  valley 
from  northern  Massachusetts  to  New  Haven  on  Long  Island 
Sound ;  another,  commencing  at  the  north  extremity  of  the  re- 
gion of  the  Palisades,  extends  through  New  Jersey  and  Penn- 
sylvania into  Virginia ;  and  others  occur  in  Virginia  and  North 
Carolina.  These  areas  are  indicated  011  the  map  on  page  136. 
DANA'S  GEOL.  STORY  —  14 


210 


MESOZOIC    TIMK. 


The  rocks  are  mainly  red  sandstones.  In  Virginia,  near 
Richmond,  and  in  the  Deep  River  region,  North  Carolina, 
there  are  beds  of  mineral  coal ;  and  those  of  the  Richmond 
basin  have  long  been  worked. 

The  beds  contain  no  marine  fossils ;  the  few  species  that 
occur  are  either  brackish-water,  freshwater,  or  terrestrial.  It 
hence  follows  that  the  long  narrow  ranges  of  sandstone  were 

FIG.  220. 


West  Rock,  New  Haven,  Conn. 
The  columnar  trap  resting  on  upturned  sandstone. 

formed  in  valleys,  parallel  with  the  Appalachians,  into  which, 
for  some  reason,  the  sea  did  not  gain  full  entrance ;  and  the 
characters  of  the  deposits  show  that  they  were  made  in  some 


KEPTILIAX    ERA.  211 

cases  in  great  marshes,  in  others  in  the  waters  of  lakes,  estu- 
aries, or  river  valleys. 

Besides  fragmental  rocks,  or  those  of  aqueous  origin,  there 
were  also  dikes  and  ridges  of  igneous  origin,  called  ordinarily 
trap  dikes  or  ridges,  from  the  rock  constituting  them. 

The  trap  of  the  various  regions  stands  up  with  a  bold  col- 
umnar front,  as  well  exhibited  in  the  Palisades,  on  the  Hudson. 
An  example  is  here  represented  in  Fig.  229,  from  West  Rock, 
in  the  vicinity  of  New  Haven,  Connecticut. 

The  trap  came  up  in  a  melted  state  from  regions  of  fusion 
below,  through  fissures.  In  the  West  Rock  view,  the  removal 
of  the  debris  below  the  base  of  the  columnar  trap  has  brought 
to  light  the  fact  that  the  stratified  sandstone  underneath  the 
trap  is  upturned. 

In  western  Kansas,  and  farther  west  over  the  Rocky  Moun- 
tain region,  red  sandstone  strata  of  great  extent,  often  contain- 
ing gypsum,  but  generally  without  fossils,  are  referred  to  the 
Triassic.  Fossils  have  been  found  in  rocks  of  this  period  in 
the  Sierra  Nevada,  California,  and  also  in  British  Columbia 
and  Alaska. 

Jurassic  beds,  with  marine  fossils,  overlie  the  Triassic  of  the 
Rocky  Mountain  region,  west  of  the  summit,  making  in  part 
the  Wasatch  Mountains,  the  Sierra  Nevada,  and  other  ranges. 

In  Great  Britain  the  Triassic  beds  (No.  6  on  the  accom- 
panying map,  Fig.  230)  were  red  argillaceous  sandstones  and 
clay  rocks  (marlytes)  formed  in  a  partly  confined  sea-basin. 
At  Cheshire  they  contain  a  bed  of  rock  salt  derived  from  the 


212 


MESOZOIC    TIME. 


FIG.  230. 


Geological  Map  of  England. 

The  areas  lined  horizontally  and  niiinbcivil  1  arc  Sihiro-Cambrian.  Those  lined  vertically 
(2),  Devonian.  Those  cross-lined  (8),  Subcarboniferous.  Carboniferous  (4),  lilack.  Per- 
mian (5).  Those  lined  obliquely  from  right  to  left,  Triassic  (0),  Lias  (7  </),  Oulyte  (11), 
Wealden  (8),  Cretaceous  (9).  Those  lined  obliquely  from  left  to  right  (Id,  11),  Tertiary. 
A  is  London  ;  B,  Liverpool  ;  C,  Manchester  ;  I),  Newcastle. 


UKPT1L1AN    ERA. 


213 


evaporation  of  the  waters  of  the  sea-basin.  The  Jurassic  rocks 
consist,  below,  of  a  limestone  called  the  Lias  (No.  7  a) ;  other 
limestones  above,  called  Oolyte  (7  &),  part  of  which  is  a  coral- 
reef  limestone,  showing  that  there  were  coral-reefs  in  the  Brit- 
ish seas  of  the  era ;  and  near  and  at  the  top  of  the  series,  fresh- 
water or  soil  beds,  called  the  Portland  dirt-bed.  The  Oolyte  is 

Fit;.  231. 


Modern  Cycad.— Cycas  circinalis  tx,,1,,). 

so  named  from  the  occurrence  of  beds  of  concretionary  lime- 
stone, made  up  of  minute  spherical  concretionary  grains  of 
the  size  of  the  roe  of  a  small  fish,  the  word  coming  from  the 
Greek  for  egg. 


214  MESOZOIC   TIME. 

As  the  Jurassic  ended  there  were  large  areas  of  dry  land 
and  marshes  in  southeastern  England. 

LIFE. 

1.  Plants.  —  The  forests  of  Early  and  Middle  Mesozoic  time, 
while  failing  of  Lepidodendra  and  related  trees  of  the  Coal 
era,  abounded  in  Tree-ferns  and  Gymnosperms,  and  especially 
Cycacls,  —  plants  that  look  like  Palms,  as  shown  in  Fig.  231  on 
page  213,  and  yet  are  true  Gymnosperms,  like  the  Conifers. 
There  were  no  Angiosperms,  —  trees  like  the  AVillow,  Maple, 
Oak,   Elm,   and    others    having    net-veined    leaves.       Conse- 
quently, wherever  Tree-ferns  and  Cycads  predominated,  the 
aspect  of  the   forest  was  very  much  like  that  of   a  modern 
grove  of  Palms. 

2.  Animals. — The  Corals  and  other  Jtatli'iitcx  hud,  for  the 
most  part,  a  general  resemblance  to  those  of  the  present  era, 
although  all  were  extinct  and  mostly  of  extinct  genera. 

One  of  the  fine  Jurassic  Crinoids,  of  Mesozoic  type,  is 
the  Pentacrinus  Briareus,  Fig.  232.  The  name  7V //Mr /•////'*, 
the  first  syllable  of  which  is  from  the  Greek  for  Jive,  refers 
to  the  five-sided  form  of  the  stem. 

The  MoHusks  also  had,  in  general,  a  modern  aspect;  and 
yet  many  kinds  were  especially  Mesozoic  in  type.  Some 
of  these,  among  the  Jurassic  Lamellibranchs,  are  repre- 
sented in  Figs.  233-237.  Fig.  233,  a  Gryphsea,  is  related 
to  the  Oyster,  but  has  the  beak  incurved,  as  the  name 
implies.  Fig.  234  is  another  oyster-like  species  having  the 


REPTILIAN    ERA. 


215 


beak  curved  to  one  side,  an  Exogyra,  the  name  refer- 
ring to  the  bend  in  the  beak.  Fig.  235  is  a  true  Oyster; 
Fig.  23G,  a  Trigonia,  the  shell  being  approximately  three- 


Fir. .  232. 


Crinoid. 
Pentacrinus  Briareus. 


sided.  Fig.  237  is  a  Diceras,  —  a  shell  in  which  both  valves 
are  prolonged  into  a  horn-like  form,  the  name  meaning  two 
horns.  Cephalopoda  were  very  abundant.  The  chambered 


216 


MESOZOIC   TIME. 


shells  of  this  tribe  were  in  vast  numbers  under  the  type  of 
Ammonoids,  while  there  were  also  many  Nautiloids.  Fig.  2.S8 
represents  a  front  view,  and  239  a  side  view,  of  one  of 


FIGS.  233-237. 


Lamellibranch  Mollusks. 

Fig.  233,  Gryphsea  incurva ;   234,  Exogyra  virgula ;    235,  Ostrea  Marshii ;   236,  Trijronia 
clavellata ;   237,  I)iccr;is  urictinum. 

the  earlier  of  the  Ammonoids,  —  a  Triassic  species.  The  ani- 
mal occupied  the  outer  chamber  of  the  shell,  as  in  the  Nautilus 
(Fig.  121,  page  131).  Fig.  238  shows  the  bottom  of  this  outer 


REPTILIAN    ERA. 


217 


chamber.     Around  its  sides  there  are  pocket-like  depressions 

into  which  the  mantle  of  the  animal 

descended  to  enable  it  to  hold   on 

to  its   shell.      Two    other    species 

of  Ammonoids  are  represented  in 

Figs.  240-242.     Fig.  241  shows  the 

pockets    in   the   outer   chamber   of 

240.     The  pockets  are  depressions 

in  the  partitions  at  their  margins. 

Fig.  242  represents  a  species  with 


Cephalopod. 
Fig.  238,   Ammonites  tornatus ;  239, 

the  outer  whorl  unbroken  and  much      side  view  of  same' reduced  one  half< 


prolonged.      In  the  Devonian  Ammonoids,  called  Goniatites, 

FIGS.  240-24-2. 


Cephalopods. 

Fig.  240,  Ammonites  Bucklandi,  from  the  Lias  ;  241,  same  in  profile,  showing  outer  cham- 
ber and  its  pockets  ;  242,  A.  Jason,  from  the  Oolyte. 

the   pockets    were  simple    in    outline;    while    those    of    the 
later  Ammonoids  are  mostly  very  complex.     Fig.    268,    page 


218 


MESOZOTC    TIME. 


FIGS.  248,  244. 


231,    shows   the    flexures    in    the    pockets    of    a    Cretaceous 

species. 

Besides  Cephalopods  with  external  shells,  there  were  also 
numerous  species,  related  to  the  modern 
Squid  (Fig.  120,  page  130)  in  having  an 
internal  bone  along  the  back,  to  give  the 
body  rigidity.  This  bone,  but  broken  at 
the  top,  is  represented  in  Fig.  243,  and 
a  perfect  one  in  Fig.  244. 

The  Vertebrates  inchided  Birds  and 
Mammals,  besides  Fishes,  Amphibians. 
and  Keptiles. 

The  Fishes  were  for  the  most  part  either 
Selachians  (Sharks)  or  Ganoids.  In  the 
Triassic  the  tail  of  the  Ganoids  was  only 
partially  vertebrated  if  at  all ;  and  in  the 
Jurassic  the  vertebrate  feature  fails  en- 
tirely, the  vertebral  column  not  extending 
into  the  tail-fin,  as  is  shown  in  Fig.  245, 
representing  a  DapecUus.  The  form  of  the 
scales  of  this  Ganoid  and  the  method  of 
Cephalopods.  interlocking  are  illustrated  in  Fig.  245  a. 

Fig.   243,   Bone   or   osselet 

of  Beiemnites  ciavatus,        f^Q  Amphibians  and  Reptiles  were  of 

broken  at  top,  from  the 

Lias ;  244,  the  bone  of   great  size  and  variety.     Respecting  Amer- 

a  Belemnite  having  its 

upper  extremity  perfect,  ican  Triassic  species  much  has  been 
learned  from  their  footprints  on  the  surfaces  of  the  finer 
layers  of  the  sandstone  of  the  Connecticut  Valley.  Some  of 


REPTILIAN   ERA. 


219 


the  largest  of  the  Reptiles  walked  as  bipeds  on  feet  that  made 
tracks  16  to  20  inches  long  and  nearly  as  broad,  and  had  a 

FIG.  245. 

^       « 


Ganoid  Fish  of  the  Genus  Dapedius. 

stride  of  three  feet.     Fig.  248  shows  the  form  of  the  tracks. 
The  impressions  o'f  the  much  smaller  fore  feet  (Fig.  248  a) 

FIGS.  246-249. 

~       r, 

/24S« 


248 


Tracks  of  Amphibians  and  Reptiles  from  the  Connecticut  Valley  Sandstone. 

Fijis.  246-247,  AMPHIBIANS  :  246,  246  a,  Anisopus  Deweyanus  (x  j) ;  247,  247  a,  A.  gracilis 
(x  |).  Figs.  248-249,  KEPTILKS  :  248,  248  a,  Otozoum  Moodii  (x  ^,)  ;  249,  249  «,  Ano- 
moepus  scambus  (x  J). 

are  occasionally  found,  showing  that  this  huge  biped  some- 
times  brought   them   to    the   ground.      Twenty-two   consecu- 


220 


MESOZOIG   TIME. 


FIG.  25l>. 


tive  tracks  of  the  hind  feet  of  one  of  these  bipeds  wen- 
laid  open  in  1874  at  the  Portland  juarries,  Connecticut. 
The  feet,  as  is  shown  in  the  figure,  were  4-toed. 

Other   species   made   3-toed   tracks   with   their    hind   feet, 
bird-like,  as  represented  in  Fig.  249. 

The  tracks  of  Amphibians  also  occur  in  the  same  region, 
and  the  hind  and  fore  feet  of  some  of  them  are  represented 
in  Figs.  246,  246  a,  and  247,  247  a.  All  the  Amphibians, 
there  is  reason  to  believe,  had  large  teeth  and  scale-covered 
bodies,  like  the  Amphibians  of  the  Carboniferous  age.  A 
tooth  of  a  related  four-footed  species  from  Europe  is  shown 
two  thirds  the  natural  size  in  Fig.  250.  The 
head  of  the  Amphibian  that  was  thus  armed  was 
over  two  feet  long,  and  three  fourths  as  broad. 
Skeletons  also  have  been  found  of  the 
Triassic  and  Jurassic  Reptiles.  In  view  of 
the  large  size  of  many  of  the  species  one 
division  has  received  the  name  of  Dinosaurs, 
from  the  Greek  for  terrible  and  lizard.  The 
tracks  of  Figs.  248,  248  a,  and  2-4  <).  249o, 
were  probably  made  by  Dinosaurs.  The  spe- 
cies had  long  legs,  not  the  creeping  legs  of 
Lizards  and  Crocodiles;  and  part  of  them,  as  the  tracks  sho\v, 
walked  in  biped  fashion,  like  Birds.  Moreover,  many  of  the 
bird-like  kinds  have  the  hind  feet  3-toed,  and  so  precisely  like 
those  of  Birds  that  they  were  at  first  called  bird-tracks. 

The  restored  skeleton  of  one  of  the  Reptiles  of  the  C'on- 


Amphibians. 

Tooth  of  Mastodon- 

saurus.    (x  J). 


REPTILIAN    ERA. 


221 


necticut  Valley,  having  hind  feet  with  three  well-developed 
toes,  the  innermost  toe  being  small,  and  the  outermost  rudi- 
mentary, from  a  quarry  not  far  from  Hartford,  is  represented 
one  twelfth  the  natural  size  in  Fig.  251 ;  and  in  Fig.  252,  one 

FIG.  251. 


Dinosaur. 

«f  Anchisaurus   colnrns  Marsh    (x  ,'5). 


of  the  5-toed  Reptiles,  quadruped-like  in  locomotion,  and  30 
feet  long,  from  the  Jurassic  beds  of  the  Rocky  Mountains. 
The  Megcdo9Ofjer  was  a  related  huge  carnivorous  species  25 


222 


MESOZOIC   TIME. 


to  30  feet  long ;  and  the  Iguanodons  and  Hadrosaurs,  equally 
large,  were  vegetable  eaters. 

The  resemblance  of  the  bipedal  Dinosaiirs  to  Birds  was 
not  merely  in  attitude  and  external  form,  but  extended  to  a 
number  of  anatomical  details  in  the  pelvis  and  the  hind  limb. 

FIG.  252. 


Dinosaur. 
Restoration  of  Brontosaurus  excelaus  (x  5*5). 

Other    Reptiles    of    the    time    were   Crocodilians,   Lizards 
(Lacertilians),    and   Turtles    (Chelonians). 
Besides   these,  large  Sea-saurians,  whale-like,  lived  in   the 

Fit;.  253. 


Ichthyosaurus  tenuirostris. 


waters,  and  flying  kinds  shared  the  air  with  the  Birds. 

The   Sea-saurians   had   paddles  like   Whales  and  were   12 
to  50  feet  long.     The  Ichthyosaurs,  or,  as  the  name  (from  the 


REPTILIAN    ERA. 


223 


Greek)  signifies,  Fish-lizards  (Fig.  253),  had  a  short  neck, 
very  large  eyes,  and  thin  vertebrse  that  were  concave  on 
both  sides,  resembling  those  of  Fishes.  Recently  discov- 
ered specimens  have  shown  that  they  possessed  a  large 
caudal  fin,  and  smaller  tins  along  the  back,  giving  the  body 
an  aspect  even  more  fish-like  than  that  of  the  Whales. 


FIG.  254. 


Sea-saurian,  Plesiosaurus  dolichodeirus  (XB\J). 
a,  one  of  the  vertebrae ;  b,  profile  of  same. 

Another    kind,   the    Plesiosaur    (meaning,    somewhat    like    a 
lizard),   had   a  long    snake-like  neck  as  represented   in   Fig. 

254,  with   a   short  body,   and   vertebrae    as    long    as    broad 
(Fig.    254  a,    6).      The  long  neck  made  it  good  at  catching 
fish  for  food. 

The  flying  Reptiles  were  called  Pterosaurs  (from  the  Greek 
for   wimjed  saurian).     One   of   them   is   represented   in   Fig. 

255,  somewhat  less  than  the  natural  size.     The  wing,  as  the 
figure  illustrates,  is  made   by   the  elongation  of  one  of  the 
fingers  and  the  expansion  of  the  skin  from  the  side  of  the  body. 


224 


MESOZOIC    TIME. 


Another  species,  from  Solenhofen,  Bavaria,  had  a  long  tail, 
with  a  bladed  extremity,  for  use  as  a  rudder ;  it  is  represented 
on  the  wing,  in  Fig.  256,  from  a  restoration  by  Professor  Marsh. 


FIG.  255. 


Pterosaur. 

Pterodactylus  spectabili.s. 


Of  Triassic  and  Jurassic  Birds,  all   that   is   known  conies 
from  two  imperfect  feathered  skeletons  found  in  the  Oolyte 


REPTILIAN    ERA. 


225 


of  Solenhofen,  and  a  fragment  of  a  skull  from  Wyoming. 
Yet,  as  the  remains  of  Birds  are  the  rarest  of  fossils  — 
because  they  are  fragile  terrestrial  species,  and  good  food 
for  all  carnivorous  life  —  these  few  specimens  are  good 
evidence  that  not  only  Europe,  but  also  the  other  con- 
tinents, abounded  in  Birds  during  the  Jurassic  period,  if 
not  earlier.  These  early  Birds  were  reptile-like  in  having 
teeth,  and  a  long  vertebrated  tail;  but  the  tail  was  feath- 
ered, it  having  a  row  of  large  feathers  along  either  side; 

FK;.  256. 


Rhamphorhynchus  phyllurus  (x  J). 

they  also  had  the  metacarpal  bones  free,  as  in  Reptiles,  not 
grown  together,  as  in  modern  Birds. 

Remains  of  Mesozoic  Mammals  have  been  found  in  the 
Triassic  beds  of  Germany  and  North  Carolina,  and  in  the 
Jurassic  of  England  and  Wyoming.  Fig.  257  represents  a 
jaw-bone  from  Xorth  Carolina,  twice  the  natural  size.  The 
species  are  of  the  lower  divisions  of  Mammals,  the  Monotremes 
and  Marsupials,  and  they  are  all  small,  like  Rats  and  Mice. 
Examples  of  modern  Marsupials  are  the  Kangaroo  of  Australia 
DANA'S  OEUL.  STORY  —  15 


226  MESOZOIC   TIME. 

and  the  Opossum  of  America.  They  are  f«'itii-(n-ijHii'ons  species, 
that  is,  kinds  whose  young  are  in  an  immature  state  when 
born,  approximating  in  this  respect  to  the  egg-stage,  an 
egg  being  an  example  of  extreme  immaturity.  They  are 
Fl(.  .i:-  peculiar  in  having  a  pouch 

(marsupium,  in  Latin),  on 
the  under  side  of  the  body, 
for  receiving  the  immature 

Dromatherium  sylvestre.  yOUllg.       Ill   addition  to  Mar- 

supials,  there  were  the  still  lower  Mammals,  the  Mouotremes, 
related  to  the  modern  Duck-bill,  or  Ornithorhynchus,  of 
Australia,  which  is  actually  oviparous,  and  lays  its  eggs  in 
holes  along  the  banks  of  streams.  The  Oniitliorhynchus 
has  the  bill  and  aquatic  habits  of  a  Duck. 

Thus,  before  the  close  of  the  Jurassic  period,  the  world 
had  its  Birds  and  Mammals;  yet  Reptiles  still  had  su- 
premacy in  magnitude,  numbers,  and  diversity  of  kinds. 

2.   Cretaceous  Period,  or  Later  Mesozoic. 
ROCKS. 

At  the  opening  of  the  Cretaceous  Period  a  subsidence  of 
the  Atlantic  borders  south  of  New  York,  and  of  the  bor- 
ders of  the  Gulf  of  Mexico  was  begun.  At  first,  fresh- 
water deposits,  called  the  Potomac  formation,  were  made 
along  the  coast.  But  afterward,  during  the  Middle  and 
Later  Cretaceous,  as  the  subsidence  increased,  the  waters  of 


REPTILIAN    ERA. 


227 


the  Atlantic  spread   over  the    border,  and  beds  with  marine 
fossils  were  made. 

This  reappearance  of  marine  conditions  along  the  old  coast 
was  a  great  event  in  geological  history ;  for  the  last  pre- 
ceding marine  beds  over  the  coast  region  were  those  of 
the  Lower  Silurian. 


North  America  in  the  Cretaceous  Period. 

Vertical  lining  indicates  submergence  during  the  Lower  Cretaceous ;  horizontal  lining,  sub- 
mergence during  the  Upper  Cretaceous ;  cross-lining,  submergence  throughout  the 
( 'retaceous. 


The  marine  beds,  moreover,  spread  widely  over  the  north- 
ern and  western  border  of  the  Gulf  of  Mexico ;  up  the 
Mississippi  Valley,  to  the  mouth  of  the  Ohio;  from  Texas 


228  MESOZOIC    TIME. 

northward  over  Kansas  and  a  large  part  of  the  eastern 
slope  and  summit  region  of  the  Rocky  Mountains,  and  prob- 
ably to  the  Arctic  Ocean.  They  extended  also  over  the 
Pacific  border  west  of  the  Sierra  Nevada. 

The  outline  of  the  continent  at  the  time  these  marine 
beds  were  in  progress  is  shown  on  the  map  on  page 
227,  Fig.  258,  the  shaded  portion  being  the  part  of  the 
land  that  was  then  under  sea-water,  receiving  Cretaceous 
deposits. 

The  Cretaceous  beds  comprise  gray  and  green  sandstones; 
compact  shell-beds  and  "  rotten "  limestone ;  hard  compact 
limestone  and  chalk  in  Texas  and  western  Kansas;  coarse 
sandstones  and  conglomerates ;  large  beds  of  clay ;  and  ex- 
tensive coal-beds. 

The  clays  in  New  Jersey,  called  Amboy  or  Earitan  clays, 
are  partly  pure  white  clays,  and  are  used  for  making  pot- 
tery and  tiles,  as  well  as  fire-bricks.  Other  kinds  burn  red 
because  they  contain  iron,  and  these  are  used  for  common 
bricks.  The  greensand  of  the  Cretaceous  is  valuable  as  a 
fertilizer.  Another  common  material  of  the  beds,  and  espe- 
cially of  the  chalk,  is  flint,  as  already  explained. 

The  coal-beds  occur  in  the  Upper  Cretaceous.  The 
coal  is  good  bituminous  coal,  much  like  that  of  the 
Carboniferous  period,  and  is  mined  at  many  places  in 
Colorado,  Utah,  Montana;  and  also  to  the  north  in  British 
America  and  to  the  west  on  Vancouver's  Island,  in  British 
Columbia. 


REPTILIAN    EKA. 


229 


LIFE. 

The  Cretaceous  period,  the  last  of  the  Mesozoic,  was  a  time 
of  transition  in  the  world's  life,  the  Vegetation,  the  Fishes, 
and  the  Birds  coming  out  under  more  modern  forms,  and  Dino- 
saurs, Pterosaurs,  and  Ammonoids  ending  with  it  their  career. 

FIGS.  259-262. 


Angiosperms  (or  Dicotyledons^. 

Fig.  259,  Liriodendron  primcevum  ;  2GO,  Sassafras  crotaceum  ;  261,  Liiiodendron  Meekil; 
262,  Sallx  Meekii. 

1.  Plants.  —  The  great  changes  in  the  vegetation  consisted 
in  the  introduction  (1)  of  Palms  and  other  related  species, 
and  (2)  of  plants  of  the  tribe  of  Angiosperms. 


230 


MESOZO1C    TIME. 


The  Angiosperms  include  the  Willow,  Elm,  Maple,  Currant, 
Rose,  and  thousands  of  species  that  are  especially  character- 
istic of  the  forests  and  prairies  of  the  present  day.  They  are 
called  Angiosperms  from  the  Greek  for  vessel  and  seed,  the 
seeds  being  covered,  as  that  of  the  Pea  or  Bean  in  its  pod,  of 
the  Walnut  in  its  husk,  and  so  on. 

Leaves  of  some  of  the  species  are  represented  in  Figs.  259- 
262.  The  leaves  of  Angiosperms  are  distinguished  from 
those  of  Cycads,  Conifers,  and  Palms  by  their  network  of 


263 


264 


FIGS.  263-266. 

a  265 

L 


Rhizopods. 

Fig.  263,  Lituola  nautlloides ;  264,  a,  Flabellina  rugosa  ;  265,  Chrysalidina  gradata  ; 
265,  a,  Cuneolina  pavonia. 


veins.  In  the  early  Cretaceous,  Cycads  and  Conifers  were  far 
the  most  abundant  species ;  but  subsequently  Angiosperms 
became  the  common  kind  and  especially  those  of  the  genera 
Liriodendron,  Magnolia,  Sassafras,  Myrtle,  Plane  tree 
(Platanus),  with  later  the  Maple,  Elm,  Oak,  Beech,  Pop- 
lar, and  other  kinds.  At  this  time  appeared  also  the  first 
of  Palms. 

The  change  was  great  in  the  foliage  of  the  forests,  and  the 
world  was  also  adorned  for  the  first  time  with  beautiful 
flowers,  and  enriched  with  edible  fruits,  —  a  promise  of  the 


REPTILIAN   ERA. 


231 


better   time    when    Birds    and    Mammals    should    be  at  the 
head. 

2.  Animals.  —  Among  Protozoans,  Rhizopods  were  very  effi- 
cient species  in  rock-making,  the  chalk  consisting  chiefly  of 
their  minute  shells.  A  few  of  the  species  are  represented, 
much  enlarged,  in  Figs.  263-266. 


FIGS.  267,  268. 


Cephalopoda. 

Fig.  26T,  Scaphites  Conradi ;  Fig.  263,  series  of  pockets  in  Ammonites  (Placenticeras) 

placenta. 


Mollnsks  continued  to  include  great  numbers  of  Ammonoids, 
and  Belemnites.  One  of  the  former  is  shown  in  Fig.  267,  and 
the  pockets  in  the  partitions  of  the  shell  of  another  common 
species  in  the  dark  parts  of  Fig.  268. 


232 


MESOZOIC    TIME. 


Fig.  269  shows  the  form  and  size  of  a  very  common  Belem- 
FIG.  269.     nite  from  the  Cretaceous  beds  of  New  Jersey. 

Fishes  were  represented  still  by  Sharks  and  Gan- 
oids. But  with  these  existed  the  earliest  unques- 
tionable examples  of  the  modern  type  of  Fishes 
called  Teleosts,  so  named  from  the  Greek  for  com- 
plete and  bone,  the  skeleton  being  bony  throughout, 
instead  of  partly  or  wholly  cartilaginous.  Salmon, 
Perch,  Herring,  Mackerel,  were  among  these  earli- 
est of  Teleosts.  The  tribe  includes  nearly  all  the 
Fishes  in  modern  waters  excepting  the  Sharks  and 
related  kinds. 

Reptiles  were  represented  by  various  Dinosaurs, 
Crocodilians,  Turtles,  Sea-saurians,  and  Flying 
Saurians.  Among  the  Dinosaurs  there  were  the 
Horned  Dinosaurs,  having  horns  like  those  of  Cat- 
tle (Fig.  270)  ;  for  the  horns  represented  in  the  figure 
are  the  cores  of  the  actual  horns.  The  species  here 
figured  was  15  feet  long.  There  were  also  Sea-ser- 
1  opo  '  pents,  called  Mosasaurs,  which  swam  by  means  of 

Belemnitella 

Americana,    paddles  and  were  15  to  50  feet  long. 

The  Flying  Saurians,  or  Pterosaurs,  resembled  much  those 
of  the  Jurassic ;  but  some  of  them  were  without  teeth, 
like  Birds.  The  largest  had  a  spread  of  wing  of  25 
feet. 

Birds  were  advanced  in  structure  through  the  loss  of  the 
low-grade  member,  a  long  tail,  and  in  acquiring  the  modern 


REPTILIAN   ERA. 


233 


structure  of   the  hand.     But   some  of    them    still   had  teeth 
along  the  jaws,  much  like  those  of  a  Reptile  (Fig.  271),  and 


FIG.  270. 


Dinosaur. 
Restoration  of  Triceratops  (x  3*5  X 

some  had  biconcave  vertebrae  like  a  Fish.     Among  the  tooth- 
less Birds  were  Cormorants  and  Waders. 

FIG.  271. 


Bird. 
Jaw  of  Hesperornis  regalis,  showing  the  teeth. 

Mammals  continued  to  include,  as  far  as  discovery  has  gone, 
only  the  feeble  Marsupials  and  Mouotrem.es,  and  the  fossils 
are  mostly  jaws,  much  like  that  figured  on  page  226. 


PROGRESS  ix  LIFE  DURIXG  THE  MESOZOIC. 

Thus  all  the  classes  of  Vertebrates  had,  in  Mesozoic  time, 
their  species.  In  the  Triassic,  its  first  period,  the  Amphibians 
passed  their  climax  in  mnnbers,  size,  and  grade,  little  being 


234  MESOZOTC   TIME. 

afterward  known  of  the  huge,  scale-covered  tribe.  But  during 
the  following  periods  Eeptiles  had  their  time  of  greatest  ex- 
pansion, the  earth,  air,  and  waters  being  in  their  possession. 
The  Birds  and  Mammals  which  appeared  in  this  age  were  only 
the  commencement  of  tribes  that  were  to  reach  their  fullest 
display  in  later  time.  Cattle  and  all  other  Placental  Mam- 
mals—  that  is,  all  ordinary  Mammals  —  were  still  in  the 
future. 

The  old  law  of  change  characterized  the  life  throughout 
Mesozoic  time.  New  fossils  are  found  in  every  successive 
rock-stratum,  and  also  older  kinds  are  missed.  The  system  of 
life  was  in  course  of  expansion  by  the  introduction  of  new 
species  and  a  casting  off  of  the  old. 

MOUNTAIN-MAKING  IN  MESOZOIC  TIME. 

The  Sierra  Nevada  and  some  ranges  to  the  north  in  British 
America  were  made  at  the  close  of  the  Jurassic.  The  strata 
of  the  mountain  region  to  the  top  of  the  Jurassic  were  folded 
up  in  the  making  of  the  mountains.  But  the  height  then 
attained,  instead  of  being,  as  now,  14,000  feet  or  more,  was 
probably  less  than  5000  feet.  At  the  same  time,  or  earlier,  the 
Triassic  rocks  of  the  Atlantic  border  in  the  Connecticut  River 
Valley  and  elsewhere  were  slowly  upturned;  and  as  the  up- 
turning made  progress,  great  fissures,  parallel  in  course  nearly 
to  the  longer  axis  of  the  areas,  were  opened  and  the 
liquid  trap  rock  came  up.  During  the  formation  of  the  sand- 


POST-MESOZOIC    REVOLUTION".  235 

stone  a  slow  subsidence  was  in  progress,  as  is  proved  by  the 
footprints  on  the  surfaces  of  layers  and  other  markings,  these 
showing  that  the  layers  —  originally  mud-flats  and  sand-flats 
—  were  successively  at  the  water  level. 

The  Post-Mesozoic  Revolution. 

The  close  of  the  Mesozoic  time  was  followed  by  mountain- 
making  on  a  grander  scale  even  than  that  with  which  Paleo- 
zoic time  was  closed  and  by  equally  extensive  disappearance 
of  species  over  the  world.  The  mountains  which  were  made 
at  this  epoch  extend  along  the  whole  line  of  the  summit  region 
of  the  Rocky  Mountains  from  near  the  Arctic  Ocean  to  Central 
Mexico  —  a  distance  exceeding  4000  miles.  They  constitute 
the  Laramide  Mountain  system,  and  include  the  Wasatch 
range  of  western  Utah ;  other  ranges  to  the  north  of  Mon- 
tana in  British  America ;  and  others  to  the  southward  over  a 
Avide  reach  of  country,  through  New  Mexico  and  Mexico  beyond. 

It  is  also  probable  that  in  South  America  at  this  same  time, 
another  system  of  ranges  of  as  great  a  length  was  made  along 
the  Andes,  and  that  consequently  the  mountain-making  move- 
ments of  America  at  the  close  of  the  Cretaceous  extended 
through  nearly  one  third  of  the  earth's  circumference. 

Until  the  beginning  of  these  movements  the  Rocky  Moun- 
tain region  was  mostly  beneath  the  salt  water ;  for  the  upper 
Cretaceous  beds  contain  marine  fossils.  Further,  during  its 
later  part,  there  were  alternate  emergences  and  submergences  of 
the  land  which  favored  the  making  of  the  many  great  coal-beds. 


23(3  I'OST-MESOZOIC    REVOLUTION. 

With  the  completion  of  the  mountains,  the  region  of  the 
great  Interior  Continental  sea  of  Cretaceous  time  made  its 
final  emergence  from  the  salt  water,  excepting  perhaps  the  area 
of  the  Great  Salt  Lake  of  Utah  and  some  other  similar  patches. 

Emergence  of  the  eastern  half  of  North  America  was  one  of 
the  great  events  at  the  close  of  Paleozoic  time;  and  so  the 
emergence  of  the  western  half  marked  the  close  of  Mesozoic 
time.  Moreover,  the  Mesozoic,  like  the  Paleozoic,  finished  its 
rock-making  work  with  the  accumulation  of  great  coal-beds  — 
the  western,  like  the  eastern,  of  incalculable  value  to  the 
country. 

The  disappearance  of  the  life  of  the  world  at  this  crisis  was 
so  extensive  that  no  marine  species  of  the  Cretaceous  period 
have  yet  been  certainly  found  in  any  rock  of  the  following 
period.  This  is  another  great  feature  in  which  the  Post-Meso- 
zoic  revolution  was  like  the  Post-Paleozoic.  Here  ended  the 
Reign  of  Reptiles,  all  the  characteristic  Mesozoic  kinds,  the 
Dinosaurs,  Sea-saurians,  Pterosaurs  or  flying  species,  and  others 
becoming  extinct.  The  Am  monoids  also,  and  the  Belemnites, 
with  many  of  the  genera  of  other  tribes  of  Mollusks,  dis- 
appeared. Among  plants,  the  Cycads,  which  were  a  prominent 
feature  of  the  Mesozoic  forests  in  the  early  Cretaceous,  even 
on  Arctic  lands,  later  retreated  southward  and  became  confined 
to  the  warm  temperate  and  tropical  zones,  where  the  few 
now  existing  are  still  to  be  found. 

As  in  other  such  exterminations,  the  extinction  of  life  was 
not  universal.  Large  regions  suffered  little  from  the  exter- 


TERTIARY    ERA.  237 

ruinating  cause,  as  the  survival  of  the  genera  and  families 
prove.  All  that  can  be  affirmed  is,  that  the  fossils  of  the  Ter- 
tiary era,  the  next  after  the  Cretaceous,  contain,  so  far  as 
yet  discovered,  no  marine  Cretaceous  species. 

IV.    CENOZOIC  TIME. 

CENOZOIC  TIME  comprises  two  eras :  — 

1.  The  TERTIARY  ERA  OR  THE  REIGN  OF  MAMMALS. 

2.  The  QUATERNARY  ERA  OR  THE  REIGN  OF  MAN. 

1.    Tertiary  Era. 

The  Tertiary  era  is  divided  into  three  periods  :  (1)  the 
EOCENE  ;  (2)  the  MIOCENE  ;  (3)  the  PLIOCENE.  These  terms, 
which  are  derived  from  the  Greek,  signify,  severally,  (1)  the 
dawn  of  recent  time;  (2)  the  less  recent;  (3)  the  more  recent. 

The  areas  over  which  the  marine  Tertiary  rocks  of  North 
America  and  England  occur  are  shown  on  the  maps,  pages 
136  and  212. 

ROCKS. 

As  the  salt  waters  had  left  the  Continental  Interior  at  the 
close  of  the  Cretaceous,  the  marine  rocks  of  the  Tertiary  were 
confined  to  the  borders  of  the  continent.  But  the  Interior  was 
still  a  region  of  extensive  rock-making  through  the  agency  of 
vast  freshivater  lakes.  The  map  on  page  238,  Fig.  272,  shows 
the  position  of  the  sea-border  Tertiary,  and  also  of  the  great 
lakes  and  litnixfrine  beds  of  the  Interior. 


238 


CENOZOIC    TIME. 


Iii  the  early  Tertiary,  the  rivers  of  the  eastern  part  of  the 
continent,  or  those  contributing  waters  and  sediment  to  the 
Atlantic,  may  have  had  half  or  two  thirds  of  their  present 


FIG.  2T2. 


Map  of  North  America  in  the  Tertiary  Period. 

Vertical  lining  shows  submergence  in  the  Eocene ;  horizontal  lining,  submergence  in  later 
Tertiary  ;  cross-lining,  submergence  throughout  the  Tertiary. 

extent;  but  the  Ohio  and  Mississippi  were  still  independent 
streams,  emptying  together  into  an  arm  of  the  Mexican  Gulf. 
The  Missouri  and  other  western  streams  were  just  beginning 
to  be. 

During  the  Eocene,  or  early  Tertiary,  the  Rocky  Mountains 
were   but    little    elevated;     for    great    lakes    then   occupied 


TERTIARY   ERA.  239 

much  of  the  summit  region,  in  Utah,  Colorado,  Wyoming,  and 
New  Mexico.  Later,  as  the  land  rose,  these  summit  lakes  dis- 
appeared, and  there  were  great  Miocene  lakes  over  what  is 
now  the  eastern  slope  of  the  mountains,  from  northern  Ne- 
braska to  Mexico.  On  the  map  the  Eocene  lakes  are  marked 
by  vertical,  the  Miocene  by  horizontal,  lines. 

The  North  American  Tertiary  consequently  comprises  vast 
freshwater  formations  as  well  as  marine. 

Marine  beds  of  the  Eocene  period  were  formed  on  the  At- 
lantic border  south  of  New  York,  and  on  the  borders  of  the 
Mexican  Gulf ;  but  marine  Miocene  and  Pliocene  only  on  the 
Atlantic  border,  from  New  York  to  Florida,  some  change  of 
level  having  excluded  them  from  the  Gulf  border  west  of  Flor- 
ida. On  the  Pacific  border  also  there  are  areas  of  marine  Ter- 
tiary. At  the  base  of  the  marine  Eocene  beds  of  the  Lower 
Mississippi  there  are  Lignitic  beds,  that  is,  beds  containing  lig- 
nite (a  kind  of  mineral  coal  retaining  usually  something  of 
the  structure  of  the  original  wood)  alternating  with  beds  that 
are  partly  marine,  the  whole  indicating  that  freshwater  marshes 
there  alternated  with  freshwater  lakes  and  salt  seas ;  for  the 
Lignitic  beds  were  once  beds  of  vegetable  debris  such  as  are 
formed  in  marshes. 

The  freshwater  Tertiary  beds  are  the  lacustrine  formations 
of  the  great  lakes  of  the  Rocky  Mountain  region  already  men- 
tioned. The  most  western  are  situated  in  Oregon.  Immense 
numbers  of  bones  of  Mammals  and  many  entire  skeletons  have 
been  obtained  from  these  beds,  showing  that  the  shores  of  the 


240  CENOZOiC    TIME. 

lakes  were  the  resort  of  wild  beasts,  some  of  them  of  elephan- 
tine size. 

In  Great  Britain  marine  Eocene  Tertiary  beds  occur  in 
the  London  and  Hampshire  basins,  and  on  eastern  seashores 
a  thin  Pliocene  stratum,  but  no  marine  Miocene  is  found. 
Over  Europe  and  Asia  the  Eocene  formation  was  widely 
distributed,  showing  that  these  continents,  even  as  late  as 
the  early  Tertiary,  were  largely  under  the  sea.  The  Pyre- 
nees, Alps,  Apennines,  Carpathians,  and  the  highest  moun- 
tains of  Asia  were  partly  made  of  them.  The  beds  in 
many  places  contain  or  consist  largely  of  coin-shaped  Fora- 
minifers,  or  Rhizopod  shells,  called  Nummulites,  varying 
from  half  an  inch  to  one  inch  or  more  in  diameter.  The 
beds  are  often  called  Niimmulitic  limestones.  The  limestone 
°^  wnicn  some  of  the  Egyptian  pyramids  are 
built  is  made  up  chiefly  of  Nummulites.  One 
of  them  is  represented  in  Fig.  273;  the  ex- 
terior is  partly  removed  to  show  the  cells  of 
Nummuiite.  the  interior,  that  were  once  occupied  by  the 
minute  Khizopods.  Some  species  of  a  related  genus 
occur  in  modern  coral  seas.  They  must  have  been  exceed- 
ingly abundant  over  the  great  Continental  seas  of  the 
Tertiary. 

Miocene  beds  have  a  thickness  of  several  thousand  feet 
in  Switzerland  (constituting  the  Bigi  and  some  other  sum- 
mits), and  occur  in  many  other  parts  of  Europe;  but  they 
are  limited  in  area  compared  with  the  Eocene.  Marine 


TERTIARY   ERA.  241 

Pliocene  beds  are  of  still  less  extent,  yet  have  a  thickness 
in  Sicily  of  3000  feet. 

The  rocks  of  the  marine  Tertiary  are  very  various  in 
kind.  The  larger  part  are  soft  sand-beds,  clay-beds,  and 
shell  deposits,  the  shells  often  looking  nearly  as  fresh  as 
those  of  a  modern  beach.  Other  beds  consist  of  moder- 
ately firm  sandstone.  There  are  also  loose  and  firm  lime- 
stones. The  greensand  called  "marl,"  used  as  a  fertilizer, 
which  is  so  characteristic  of  the  Cretaceous,  also  constitutes 
beds  in  the  Tertiary  of  New  Jersey. 

The  freshwater  beds  are  like  the  softer  marine  beds,  but 
contain,  of  course,  no  marine  shells.  Part  of  them  are  quite 
firm ;  but  others  are  easily  worn  by  the  rains.  Some  great 
areas  in  the  Rocky  Mountain  region,  both  over  the  sum- 
mit and  the  eastern  slope,  have  been  reduced  by  denuding 
waters  to  areas  of  isolated  ridges,  towers,  pinnacles,  and 
table-topped  hills,  that  are  mostly  barren,  owing  to  the  dry 
climate,  and  which  are  therefore  called  "Bad  Lands,"  or  in 
French  (in  which  language  the  expression  was  first  applied), 
"Mauvaises  Terres." 

LIFE. 

The  life  of  the  Tertiary  shows  in  all  its  tribes  an  ap- 
proximation to  that  of  the  present  time.  The  Mammals, 
and  probably  the  Birds,  are  all  of  extinct  species.  But 
among  the  plants  and  the  lower  orders  of  animals  there 
were  many  species  that  still  exist :  in  the  Eocene,  a  small 
DANA'S  GEOL.  STORY  — 16 


242 


CENOZOIC    TIME. 


percentage;  in  the  Miocene,  25  to  40  per  cent;  and  in  the 
Pliocene,  a  much  larger  proportion.  The  common  Oyster 
was  living  in  the  Pliocene,  and  the  Clam  as  far  back  as 
the  Miocene  period,  along  with  a  large  number  of  species 
of  shells  that  are  now  extinct.  Progress  through  the 
Tertiary  era  was  gradual  in  all  departments. 


FIGS.  274-2T8. 

278 


Eocene  of  Alabama. 


Fig.  274,  Ostrea  sella'formis  ;  275,  Oassatella  alta ;  276,  Pteropsis  Couradi ;  277,  Venericar- 
dia  planicosta ;  278,  Turritella  carinata. 

The  forests  of  North  America  and  Europe  were  much  like 
the  modern,  but  with  a  larger  proportion  of  warm-climate 
forms,  especially  in  the  Early  Tertiary.  Through  the 
Eocene,  Palms  nourished  over  Europe  and  England.  In 
the  Miocene  the  European  species  were  still  those  of  a 
warmer  climate  than  the  present,  and  included  some  Aus- 
tralian species.  Even  in  the  Arctic  zone  there  were  in  the 
Miocene  great  forests  of  Beech,  Oak,  Poplar,  Walnut,  and 


TERTIARY   ERA. 


243 


Redwood  (or  Sequoia,  the  genus  to  which  the  "  great  trees " 
of  California  belong),  with  Magnolias,  Alders,  and  others. 


FK.S.  -279-2S1. 


FIG.  282. 


Miocene  of  Virginia. 
Figs.  279,  280,  Oepidula  costata ;  281,  Cypriea  Carolinensis. 

The  modern  aspect  of   the   marine  shells  is  shown  in  the 
accompanying  figures:     Figs.  274- 
278    represent    American     Eocene 
species,  and  279-281,  Miocene  from 
the  Atlantic  border. 

The  Tertiary  Vertebrates  were 
less  like  the  modern  than  the  Inver- 
tebrates. Among  Fishes,  Sharks 
were  exceedingly  abundant,  and 
their  teeth,  the  most  enduring  part 
of  the  skeleton,  are  very  common 
in  some  of  the  beds.  Those  of 
one  kind,  pointed,  triangular  in 
form,  were  nearly  as  large  as  a  man's  hand.  One  of  the 
smaller  of  these  teeth  is  represented  in  Fig.  282. 


Shark's  Tooth. 
Carcharodon  angustidens. 


244 


CENOZOIC   TIME. 


The  true  Reptiles  were  Crocodiles,  Lizards,  Turtles,  some 
of  gigantic  size,  and  Snakes. 

Among  the  Birds  there  were  Owls,  Woodpeckers,  Cormo- 
rants, Eagles ;  and  those  of  France  included  Parrots,  Trogons, 
Flamingoes,  Cranes,  Pelicans,  Ibises,  and  other  kinds  related 
to  those  of  warm  climates. 

The  common  Mammals  were  the  ordinary  non-Marsupial 
kinds.  The  Eocene  beds  about  Paris,  France,  afforded  to 

FIG.  283. 


Tapirus  Indicus,  the  Modern  Tapir  of  India. 

Cuvier  the  first  specimens  described;  and  now  they  are 
known  from  all  parts  of  the  world,  and  from  none  in  greater 
variety  than  from  the  freshwater  Tertiary  region  west  of 
the  Mississippi. 

Some  of  the  Eocene  kinds  were  related  to  the  modern 
Tapir  (Fig.  283),  Hog,  Rhinoceros,  and  Hippopotamus. 

The  earliest  species  appear  to  have  had  the  full  number  of 
toes,  Jive,  to  both  the  fore  and  hind  feet,  typical  of  Mammals, 


TERTIARY    ERA. 


245 


and  also  the  full  number  of  teeth,  forty-four ;  while  most  of 
the  later  species  have  a  less  number  of  teeth,  and  most  of  the 
hoofed,  or  ungulate,  species,  and  some  of  the  clawed,  or  un- 
guiculate,  species,  have  a  less  number  of  toes.  The  Tapir, 
here  figured,  has  three  toes  behind  and  four  in  front;  and 
the  Hog  and  Hippopotamus,  each  four  to  all  the  feet;  Cam- 
els, Cattle,  and  Sheep,  two  to  each  foot;  and  the  modern 
Horse,  but  one. 


FIG.  2<4. 


Tinoceras  ingens. 

One  of  the  strange  beasts  of  the  Eocene  is  represented  in 
Fig.  284.  It  had  three  pairs  of  horns,  feet  somewhat  like  those 
of  an  Elephant,  and  a  length,  exclusive  of  the  tail,  of  12  feet. 

The  Miocene  beds  of  North  America  have  afforded  remains 
of  3-toed  Horses,  of  extinct  species  related  to  the  Tiger, 
Wolf,  Rhinoceros,  Camel  or  Llama  (Fig.  285),  Deer,  Masto- 
don, Squirrel  and  Beaver. 


246 


CENOZOIC    TIME. 


In  the  Pliocene  beds  of  North  America  occur  remains  of 
true  one-toed  Horses,  Camels,  Mastodons,  and  various  other 
species — all  of  them  extinct,  like  those  of  the  Miocene  and 
Eocene.  In  the  Pliocene  of  other  lands  occur  species  of 
Elephant,  Bear,  Horse/  Antelope,  Stag,  Sheep,  Ox,  etc.  Cat- 
tle related  to  the  Ox  do  not  occur  earlier  than  the  Pliocene. 

The  Mammalian  type  was  at  last  very  fully  displayed,  its 

FIG.  285. 


Poebrotherium  labiatum. 

grand  divisions  and  most  of  the  modern  genera  being  well 
represented.  But  the  maximum  display  of  the  brute  races 
took  place  stitt  later,  in  the  early  or  middle  Quaternary,  after 
Man  had  appeared. 

MOUNTAIN-MAKING  DURING  THE  TERTIAKY. 

During  the  later  part  of  the  Tertiary,  the  loftiest  moun- 
tains of  the  world  received  the  greater  part  of  their  present 
elevation. 


TERTIARY   ERA.  247 

Iii  North  America,  the  amount  of  actual  upturning  was 
small  compared  with  that  at  the  close  of  the  Cretaceous 
period.  There  were  low  mountains  made  after  the  Miocene 
on  the  coast  region  of  the  Pacific ;  •  and  some  of  the  Mio- 
cene lacustrine  areas  were  upturned.  But  besides  these 
local  events,  a  lifting  of  the  Rocky  Mountains  as  a  whole 
from  the  far  North  to  Central  America  was  begun,  which 
continued  on  through  the  Tertiary  and  ended  in  raising 
the  great  area  from  near  the  sea  level  —  where  it  was,  as 
fossils  prove,  at  the  close  of  the  Cretaceous  period  —  to  a 
height  of  10,000  feet  above  it  in  Mexico,  16,000  feet  in 
Colorado  (nearly  2000  feet  of  this  height  since  lost  by  de- 
nudation), and  10,000  to  4000  feet  in  British  Columbia. 
The  existence  of  vast  freshwater  lakes  over  the  Rocky 
Mountain  region  proves  that  the  rising  went  forward  with 
extreme  slowness,  and  probably  with  long  intervals  of  delay; 
that  little  progress  was  made  in  the  Eocene  period,  when 
the  lakes  covered  the  summit  region;  and  that  the  final 
height  was  not  attained  before  the  close  of  the  Pliocene, 
the  last  period  of  the  Tertiary.  During  the  same  time 
the  Andes  received  an  addition  to  their  height  of  20,000 
feet  in  Ecuador  and  of  many  thousands  in  less  elevated 
portions. 

In  Europe  the  Pyrenees  experienced  extensive  upturnings 
near  the  close  of  the  Eocene,  and  the  Alps  and  Juras  after 
the  Miocene ;  and  now  the  rocks  before  submerged  are  10,000 
and  12,000  feet  above  sea  level.  In  Asia,  upturning  began 


248  CENOZOIC    TIME. 

in  the   Himalayas,   after   the   Miocene,  and  a  rise   followed 
of  20,000  feet. 

During  Tertiary  time,  moreover,  and  especially  in  the 
Miocene  period,  great  eruptions  of  igneous  rocks  took  place 
over  the  western  slope  of  the  Rocky  Mountains,  covering 
thousands  of  square  miles.  The  deep  fractures  were  prob- 
ably then  opened  which  gave  origin  to  the  volcanoes  Mount 
Shasta,  Mount  Hood,  and  other  summits  in  the  Cascade 
range.  So  also  along  the  coast  of  Ireland  and  of  Scotland, 
and  the  Inner  Hebrides  to  the  Faroe  Islands,  the  eruptions 
were  of  great  extent.  Fingal's  Cave  and  the  Giant's  Cause- 
way date  from  this  period. 

This  epoch  of  great  eruptions  in  the  Rocky  Mountains  ap- 
pears to  have  begun  before  the  close  of  the  Cretaceous  period, 
and  to  have  had  a  climax  during  the  making  of  the  Laramide 
Mountain  system.  At  this  time  also  the  rich  silver  and  lead 
veins  of  the  Rocky  Mountains,  from  Wyoming  to  central 
Mexico,  were  probably  made ;  and  probably  also  those  of 
like  character  and  richness  along  the  Andes.  The  eruptions 
of  the  Miocene  period,  however,  seem  to  have  been  on  a 
still  larger  scale.  The  great  Continental  uplifting  of  the 
closing  Tertiary  was  a  prelude  to  the  grand  events  of  the 
opening  Quaternary. 

CLIMATE. 

During  Mesozoic  time  the  Arctic  zone  was  warm  enough 
for  great  Reptiles,  —  warm-climate  species ;  and  the  British 
seas,  for  coral-reefs. 


QUATERNARY    ERA.  249 

The  Eocene  era  also  was  one  of  warm  climate  over  Great 
Britain,  —  for  England  was  then  a  land  of  Palms ;  and  Palms 
continued  to  flourish  over  middle  and  southern  Europe  during 
the  Miocene.  Through  both  the  Eocene  and  Miocene  the 
Arctic  lands  were  covered  with  forests,  and  hence  the  Arctic 
climate  must  have  been  comparatively  warm,  —  not  colder  at 
least  than  the  present  climate  of  the  middle  United  States 
and  northern  Prussia.  There  was  a  cooling  off  with  the 
progress -of  the  Miocene,  and  by  the  close  of  the  Tertiary  the 
earth  had  probably  its  frigid,  temperate,  and  torrid  zones, 
nearly  as  now. 

2.     Qimt<'i-n<t.rn  Era. 

The  geological  work  of  the  Quaternary  was  widely  different 
from  all  that  had  preceded  it  in  the  earth's  progress.  With  the 
close  of  the  Tertiary,  the  continent  which  was  begun  in  the 
nucleal  V  of  Archaean,  time  (map,  page  139,  Fig.  124)  was  fin- 
ished out  very  nearly  to  its  present  limits ;  and  at  its  close  the 
Tertiary  formation  of  the  sea-border  was  added  to  the  dry  land. 

This  accomplished,  the  Quaternary  opened.  Agencies  were 
now  at  work  over  the  broad  surface  of  the  continent  —  its  dry 
land,  and  not  its  Continental  seas,  as  formerly,  —  transporting 
southward  gravel  and  earth  from  regions  to  the  north,  in  order 
to  cover  the  hills  with  gravel  and  soil  and  fill  the  valleys  with 
alluvial  plains.  Over  large  areas  in  both  Europe  and  America 
transportation  went  forward  from  the  high  latitudes  south- 
ward, except  where  there  were  mountains  sufficiently  lofty 


250  CENOZOTC    TIME. 

to  be  sources  of  independent  movements.  Hills  and  valleys 
were  no  impediment  to  the  great  agent  engaged  in  this 
immense  continental  system  of  transportation.  The  aid  of 
the  ocean  was  not  needed  in  these  movements,  and  was  not 
given  except  to  a  small  extent  along  its  borders. 

After  these  great  results  were  attained,  the  more  quiet  work 
of  the  rivers  went  forward ;  and  finally,  through  this  and  other 
agencies,  in  connection  with  some  change  of  continental  level, 
the  earth  assumed  slowly  its  present  perfected  condition  of 
surface  and  climate. 

The  age  .is  divided  into  three  periods:  (1)  the  GLACIAL 
period;  (2)  the  CHAMPLAIN  period;  (3)  the  BECENT  or  TER- 
RACE period.  The  Glacial  and  Champlain  periods  are  also 
called  together,  the  PLEISTOCENE  period. 

1.    Glacial  Period.  —  The  general  facts  are  these  :  — 

1.  Glacial  Phenomena.  —  In  America  and  Europe,  over  the 
northern  latitudes,  sand,  gravel,  stones,  and  masses  of  rock 
hundreds  of  tons  in  weight  are  found,  from  a  few  miles  to 
a  hundred  and  more,  south  of  the  region  whence  they  were 
derived.  This  transported  material  is  called  drift,  and  the 
stones  or  rocks,  bowlders. 

In  North  America,  the  region  over  which  the  transportation 
took  place  embraced  the  whole  surface  of  the  more  northern 
latitudes  from  Labrador  or  Newfoundland  to  the  eastern  part 
of  Nebraska ;  and  it  extended  southward  to  the  parallel  of 
40°  north  latitude,  and  beyond  this  in  Illinois,  Kansas,  and 
Missouri. 


90  85  80     I         75  70 

H    U    D    S    O 


1    MAP OF 

NORTH  AMERICA 

ILLUSTRATING  THE  PHENOMENA 

OF  THE 

GLACIAL  AND  CHAMPLAIN 
PERIODS 


Limit  of  ice  sheet 
Moraines 

• 


ean  direction  of  Glacial  \\\  \ 

cratches  *  * 

Former  shore  line  of  lakes 


252  CENOZOIC   TIMK. 

It  also  included  the  summit  regions  of  the  Rocky  Mountains 
in  British  America  and  locally  their  continuation  for  some 
distance  in  the  United  States ;  also  the  region  farther  west  in 
British  America,  the  higher  summits  of  Washington  and 
Oregon,  with  portions  of  the  Sierra  Nevada  in  California. 

In  Europe  the  mountains  of  Scandinavia  were  the  chief 
source  from  which  the  drift  was  distributed.  It  extended 
thence  southwestward  over  much  of  the  British  Islands; 
over  northern  Europe,  to  the  parallel  of  50°,  where  the 
temperature  is  about  the  same  as  along  the  parallel  of  40° 
in  North  America;  and  eastward  over  Russia  beyond  the 
Urals.  The  region  of  the  Alps  was  one  of  the  local  glacial 
areas,  and  those  of  the  Pyrenees  and  Caucasus  were  others. 
The  direction  of  travel  was  generally  to  the  southeastward, 
southward,  or  southwestward. 

The  fact  and  the  direction  of  transportation  have  been 
ascertained  by  tracing  the  stones  to  the  ledges  from  which 
they  were  derived.  Thus  bowlders  of  trap  and  red  sand- 
stone from  the  Connecticut  Valley  are  found  on  Long  Island, 
and  masses  of  granite,  gneiss,  quartzyte,  and  other  rocks  in 
New  England,  to  the  southward  or  southeastward  of  the 
ledges  that  afforded  them.  In  the  same  manner  masses  of 
granular  limestone,  or  marble,  have  been  proved  to  have 
come  from  a  formation  50  or  100  miles  to  the  northward  of 
their  present  position.  So  again  masses  of  native  copper 
are  found  in  Indiana,  Illinois,  and  Iowa,  that  were  brought 
from  the  veins  of  native  copper  south  of  Lake  Superior. 


QUATERNARY    ERA. 


253 


The  greatest  distance  to  which  bowlders  have  been  traced 
has  been  400  or  500  miles  in  Europe,  and  200  to  400  over 
eastern  North  America. 

These  bowlders  are  sometimes  over  50  feet  long,  and 
contain  more  than  20,000  cubic  feet,  so  that  they  compare 
well  in  size  with  large  houses. 

Drift  regions  are  also  regions  of  extensive  planings,  pol- 
ishings,  and  scratchings  of  the  rocks  (Fig.  287).  These 

FIG.  287. 


Drift  Scratches  and  Planings. 

scratches  may  be  found  in  them  almost  anywhere  on  hard 
rocks  that  have  been  recently  uncovered.  Vast  areas  are 
thus  scoured  and  scratched  over,  and  the  scratches  have 
great  uniformity  in  direction.  The  transported  bowlders 
and  stones  also  are  scratched. 

Scratches  and  bowlders  occur  on  top  of  Mount  Mansfield, 
the  highest  point  in  the  Green  Mountains,  4430  feet  above 
the  sea,  and  bowlders  at  a  level  of  6290  feet  011  the  White 


254  CENOZOIC   TIME. 

Mountains  in  New  Hampshire ;  and  the  direction  of  the 
scratches  as  well  as  of  the  bowlder-travel  shows  that  the 
transporting  agent  moved  over  both  of  these  summits  with- 
out finding  in  them  any  serious  impediment,  and  thence 
continued  on  its  way  southeastward. 

The  drift  covers  the  mountains  and  hills  of  drift  regions, 
and  makes  also  a  large  part  of  the  formations  in  the  val- 
leys. Over  the  hills  it  is  unstratified  drift,  called  also  till, 
the  sands,  gravel,  and  stones  having  gone  down  pell-mell 
together ;  in  river  valleys,  where  within .  reach  of  the 
waters,  it  is  stratified  drift,  —  stratified  because  there  the 
sands  and  gravel  were  deposited  in  flowing  water,  which 
assorted  somewhat  the  material  and  spread  it  out  in  beds. 
In  drift-covered  regions  the  excavations  for  the  cellars  of 
houses  are  often  made  in  the  stratified  drift,  and  the  sands 
usually  show  a  succession  of  beds  which  is  evidence  of  the 
action  of  water. 

2.  Cause  of  the  Glacial  Phenomena.  —  No  known  agent  is 
adequate  for  transportation  on  so  vast  a  scale  except  mov- 
ing ice;  and,  as  Agassiz  was  the  first  to  appreciate,  it  was 
ylacier  ice.  The  size  of  the  blocks  transported  is  no  greater 
than  of  those  now  borne  along  on  the  backs  of  glaciers;  and 
the  planing  and  scratching  is  just  what  the  Alps  everywhere 
exemplify.  The  moraines  of  the  glaciers,  as  explained  on 
page  82,  are  derived  in  the  Alps  from  the  cliffs  either  side 
of  the  ice-stream,  and  a  small  part  only  is  taken  up  by 
the  abrading  surface  at  the  bottom.  In  the  Continental 


QUATERNARY    ERA.  255 

glacier  of  the  Glacial  period,  the  stones,  gravel,  and  sand 
were  gathered  from  the  hills  over  which  the  ice  moved,  for 
there  were  110  cliffs  or  peaks  projecting  above  the  surface 
even  in  hilly  New  England  and  rarely  any  in  other  north- 
ern states.  The  White  Mountains,  as  before  remarked,  have 
bowlders  at  a  height  of  6290  feet,  or  almost  at  the  very 
summit  point,  and  therefore  they  were  buried  in  the  great 
glacier.  Taking  the  height  at  the  White  Mountains  as  a 
guide,  the  upper  surface  of  the  glacier  at  that  point  was 
at  least  6500  feet  above  the  sea  level.  From  this  region  the 
ice-surface  sloped  away  over  southern  and  southeastern  New 
England  to  its  place  of  discharge  in  the  Atlantic.  Over  the 
Adirondacks,  the  height  was  even  greater;  for  it  was  suffi- 
cient for  the  transportation  of  drift  and  bowlders  across  the 
Green  Mountains,  southeastward. 

A  thickness  of  even  2000  feet,  which  is  over  four  times 
that  of  the  largest  Alpine  glacier,  would  have  given  great 
abrading  power  to  the  heavy  mass.  All  soft  or  decomposed 
rocks  over  which  it  moved  would  have  been  deeply  worn 
down  by  it,  and  hard  rocks  with  open  joints  or  planes  of 
fracture  would  have  been  torn  to  pieces.  The  heavily  press- 
ing, slowly  moving  mass  would  have  taken  the  loose  and 
loosened  rock-material  that  lay  over  the  hills  beneath  into 
itself,  as  additional  freight  for  transportation. 

Masses  of  trap  500  to  1200  tons  in  weight  lie  along  the 
elevated  western  border  of  the  plain  of  New  Haven  in 
Connecticut,  which  were  gathered  up  from  the  trap  hills 


256  CENOZOIC  TLMK. 

between   Meriden  and   Mount   Tom  in  Massachusetts.      The 

highest  of  these  hills  are  about  1000  feet  high  above  sea, 
level,  and  their  tops,  when  the  masses  were  taken  up,  were 
300  to  1000  feet  above  the  level  of  the  adjoining  valleys. 

A  glacier  moves  in  the  direction  of  the  slope  of  its  nj>i>cr 
surface,  in  spite  of  the  slope  of  the  surface  beneath  it.  It 
is  like  thick  pitch,  as  well  as  water,  in  this  respect.  If 
pitch  were  dropped  indefinitely  over  a  spot  in  a  plain,  it 
would  spread  away  indefinitely;  and  if  the  surface  around 
the  spot  even  had  a  rising  slope,  it  would  fill  up  the  basin 
and  then  take  a  course  outward.  80  it  is  with  the  ice  of 
a  glacier.  In  order  to  have  a  southeastward  course,  a  glacier 
must  have  its  surface  highest  to  the  northwestward,  with 
slope  southeastward;  and  if  the  snows  were  more  abundant 
to  the  north  in  the  Glacial  era,  and  the  melting  less  abun- 
dant there  than  to  the  south,  an  accumulation  to  the  north 
might  have  gone  on  that  would  have  produced  movement 
southward.  If  the  plane  beneath  the  pitch  had  deep  chan- 
nels obliquely  crossing  it,  the  pitch  in  these  channels  would 
follow  their  direction,  while  the  overlying  pitch  kept  on  its 
main  course.  So  with  the  glacier, — its  lower  part  within  the 
large  valleys  followed  the  directions  of  the  valleys,  as  the 
scratches  and  bowlders  show ;  while  the  upper  portion  had 
its  iisual  course,  the  course  which  is  indicated  by  the 
scratches  elsewhere  over  the  higher  parts  of  the  country. 

The  cold  of  the  era  may  have  been  mainly  due  to  an  eleva- 
tion and  extension  of  Arctic  lands,  increasing  the  area  of 


QUATEKNAUY    ERA.  257 

Arctic  land-ice ;  and  to  a  partial  closing,  through  this  eleva- 
tion, of  the  Arctic  region  against  the  warm  current  of  the 
Atlantic  Ocean,  —  the  Gulf  Stream  which  is  now  a  source  of 
warmth  to  all  of  northeastern  Europe,  and  even  Iceland, 
Nova  Zembla,  and  the  polar  seas  and  lands.  But  it  is  prob- 
able that  the  land  of  the  higher  latitudes  of  America  and 
Europe  was  higher  than  now ;  and  that  the  Antarctic  region 
was  an  area  of  high  land;  and  that  this  was  a  prominent 
cause  of  the  cold.  Other  reasons  for  cold  have  been  suggested, 
references  to  which  will  be  found  in  large  works  on  the  subject. 

South  America  has  in  its  southern  portion  a  great  glacial 
region,  bearing  evidences  of  transportation  toward  the  equa- 
tor; and  farther  north  there  were  glaciers  about  the  higher 
summits  of  the  Andes.  The  phenomena  described  were  there- 
fore not  confined  to  one  hemisphere.  Some  writers  suppose 
them  to  have  occurred  alternately  in  the  northern  and  the 
southern  hemisphere.  But  no  direct  evidence  of  this  has 
been  obtained. 

The  moving  glacier  of  New  England  appears  to  have  had  its 
head  in  the  height  of  land  between  the  St.  Lawrence  Valley 
and  the  Great  Lakes  on  the  south,  and  Hudson  Bay;  for  the 
scratches  diverge  from  this  region  over  eastern  Maine,  New 
Hampshire,  Vermont,  and  New  York,  being  in  western  New 
York  and  Pennsylvania  southwest  in  direction.  Over  this 
region  the  ice  appears  to  have  reached  its  highest  elevation. 
This  ice-plateau,  called  the  Laurentide  plateau,  extended  west- 
ward, and  also  northward  by  the  west  side  of  Hudson  Bay,  and 
DANA'S  GEOL.  STORY  — 17 


258 


CENOZOIC    TIME. 


from  it  the  ice  descended  with  its  freight  of  stones  and  gravel 
southwestward  over  Michigan,  Wisconsin,  Illinois,  and  Iowa, 
reaching  even  into  Kansas  and  Missouri ;  and  westward  cross- 
ing the  Winnipeg  region  to  where  the  ice  met  that  of  the 


View  on  Roche-Moutonnee  Creek,  Colorado. 

summit  of  the  Rocky  Mountains.  North  of  Hudson  Bay  and 
of  60°  to  65°  in  western  North  America,  the  flow  was  north- 
ward. 

Local  glaciers  of  great  magnitude  existed  about  the  higher 
parts  of  the  Rocky  Mountains,  within  the  United  States,  and 
also  on  the  Sierra  Nevada.  Moraines,  scratches,  roches  mou- 
tonnees,  on  a  grand  scale  occur  in  many  valleys  of  the 


QUATERNARY    ERA  '259 

higher  ridges  of  both  the  Rocky  Mountains  and  the  Sierra  Ne- 
vada, as  mementos  of  their  former  Glacial  history.  The  sketch 
(Fig.  288,  page  258)  of  roches  moutonnees  in  one  of  the  higher 
valleys  of  Colorado  is  repeated  here  from  page  82,  because  the 
events  indicated  belong  to  the  Glacial  period.  The  roches 
moutonnees  extend  along  the  valley  through  an  ascent  of 
nearly  2000  feet.  At  present  there  are  no  glaciers  within  500 
miles  of  the  place. 

In  the  same  era  a  glacier  in  the  Alps  buried  all  Switzerland, 
2000  to  4000  feet  deep  in  ice,  and  left  immense  blocks  of 
Alpine  rocks  on  the  Jura  Mountains. 

Depositions  of  earth  and  stones  from  the  glacier  must  have 
been  going  on  to  some  extent  through  the  whole  Glacial  era. 
Moreover,  the  perpetual  grinding  of  stones  against  stones  under 
a  glacier  often  made  a  very  fine  clayey  earth;  and  consequently 
the  drift  is  often  called  bowlder-clay. 

3.  Retreat  of  the  Ice.  —  The  southern  ice-limit,  when  the  ice 
was  of  maximum  extent,  reached,  on  the  east,  to  southern 
Long  Island;  thence  it  continued  westward,  by  Perth  Am- 
boy,  New  Jersey;  crossed  Pennsylvania  obliquely;  and  fol- 
lowed nearly  the  course  of  the  Ohio  River  from  Ohio  to  and 
across  the  Mississippi.  West  of  the  Missouri  it  bent  north- 
ward and  westward  to  North  Dakota,  and  then  westward 
to  Montana,  where  it  reached  the  ice  of  the  Rocky  Moun- 
tains, about  4000  feet  below  the  summit.  The  position  of 
this  southern  limit  of  the  ice  is  shown  by  the  line  AA  on 
the  maps  on  pages  251  and  200. 


For  explanation  of  the  map  see  pace  251. 


QUATERNARY    ERA.  261 

At  the  melting,  the  retreat  first  showed  progress  in  the 
Continental  Interior,  over  Illinois,  Kansas,  and  Iowa,  where 
the  land  was  laid  bare  by  the  melting,  in  Illinois  and  Iowa, 
for  250  miles  northward  from  the  southern  limit,  before 
there  was  much  appreciable  change  in  Pennsylvania  and 
to  the  eastward.  This  difference  in  rate  of  melting  was 
owing  to  the  fact  that  the  east  was  a  region  of  great  pre- 
cipitation, where,  therefore,  snows  were  freely  supplied 
to  keep  the  ice  up  to  its  limit;  while  the  Interior  was  dry, 
a] id  the  small  amount  of  snow  of  the  year  was  easily 
melted. 

From  Kansas  over  eastern  Nebraska,  in  or  near  the  Mis- 
souri Valley,  the  first  retreat  extended  northward  for  1000 
miles  or  more,  reaching  far  into  British  America.  As  a 
consequence  of  the  melting  along  this  1000  miles,  the  Mis- 
souri was  at  this  epoch  the  great  river  of  the  continent, 
with  the  lower  Mississippi  as  its  seaward  continuation. 

After  a  long  halt,  the  melting  again  became  so  great  that 
the  retreat  began  anew.  Over  the  northern  part  of  the 
Continental  Interior,  the  margin  was  moved  eastward  to  and 
across  Lake  Winnipeg;  and  from  Minnesota,  Wisconsin,  and 
Michigan,  it  was  moved  northward  into  British  America. 
Then  the  Mississippi  became  the  greatest  of  rivers;  for  the 
elevation  of  the  land  to  the  north  was  such  that  the  Win- 
nipeg waters  poured  down  the  Red  River  of  the  North  and 
the  Minnesota  River  in  great  volumes  to  fill  up  and  flood 
the  Mississippi. 


262  CENOZOIC   TIME. 

Finally,  Neiv  York  and  New  England  lost  their  ice,  ex- 
cepting what  lingered  about  the  higher  mountains. 

The  melting  is  evidence  of  a  slow  change  of  climate.  It 
may  have  begun  in  consequence  of  changes  outside  of  the 
continent.  But  before  it  was  completed  there  was  a  sub- 
sidence of  the  land  over  the  higher  latitudes,  which  made 
the  climate  still  warmer,  and  so  hastened  the  disappearance 
of  the  ice. 

With  this  subsidence  a  new  period  opens  in  the  earth's 
history  —  characterized  by  a  mild  climate,  even  milder  than 
that  now  existing;  and  by  a  reforesting  and  repopulating 
of  the  previously  glaciated  regions. 

2.  Champlain  Period.  —  The  warm  Champlain  period,  in 
strong  contrast  with  the  period  of  slow-moving  ice,  was  the 
time  of  great  floods  along  the  river  valleys,  as  a  conse- 
quence (1)  of  the  waters  let  loose  by  the  lingering  ice  of  the 
hills,  and  also  (2)  of  excessive  rains  from  the  continued  moist 
climate. 

In  further  contrast  with  the  Glacial  period,  it  was,  as 
has  been  stated,  a  time  of  lower  level  than  now  over  the 
higher  latitudes ;  and  hence  the  action  of  the  rivers  became 
changed  to  a  large  extent  from  excavating  streams,  deepening 
thereby  their  channels,  to  streams  that  deposited  sediment 
along  their  banks,  and  thereby  made  great  fluvial  formations. 
As  a  consequence,  moreover,  of  the  genial  climate,  the 
banished  forests  and  animal  life  rapidly  regained  possession 
of  the  plains  and  hills. 


QUATERNARY   ERA.  263 

The  fact  that  the  land  of  the  more  northern  latitudes  was  at 
a  lower  level  than  now  is  proved  by  the  existence  of  many 
Cliamplain  sea-beaches  or  marine  beds  at  high  levels,  in  the 
form  of  terraces,  along  the  existing  borders  of  the  ocean, 
lakes,  and  rivers.  The  beds  have  a  height  of  80  feet  on  Nan- 
tucket ;  150  to  300  along  the  coast  of  Maine ;  300  to  600  along 
the  St.  Lawrence  Valley,  —  the  greatest  height  up-stream, 
namely,  200  feet  at  its  mouth,  520  feet  at  Montreal,  and  600 
not  far  from  Lake  Ontario,  so  that  the  St.  Lawrence  River 
was  then  a  vast  St.  Lawrence  Gulf,  500  to  600  feet  deep. 
Even  Lake  Champlain  was  an  arm  of  this  St.  Lawrence  Gulf, 
for  beaches  containing  sea  shells  occur  on  its  borders  to  a 
height  of  450  feet,  and  at  a  little  lower  level  remains  of  a 
whale  have  been  found.  It  had  the  great  depth  of  from  700 
to  900  feet.  Moreover,  Labrador  has  similar  beaches  at  a 
height  of  500  to  800  feet,  and  some  Arctic  land  at  1000  feet. 
Similar  facts  are  reported  from  the  Pacific  coast. 

The  subsidence  was  greatest  to  the  north,  it  having  been 
probably  not  over  twenty  feet  on  Long  Island  Sound,  and 
seventy  at  New  York  Bay,  while  it  was  500  feet  at  Montreal 
and  335  feet  at  Albany,  New  York.  This  increase  to  the  north- 
ward was  the  cause  of  the  diminished  pitch  in  most  of  the 
rivers ;  for  it  affected  directly  all  southward-flowing  streams. 

The  deposits  from  the  flooded  waters  along  the  valleys 
and  about  the  lakes  became  hundreds  of  feet  thick  in 
many  places.  The  upper  flat  surface,'  now  the  "upper 
terrace "  of  the  valley,  is  a  mark  approximately  of  flood 


264  CENOZOIC   TIME. 

height.  The  valleys  of  the  Hudson  and  the  Connecticut 
are  examples. 

The  waters  gathered  their  detritus  from  the  drift-covered 
hills  through  their  numerous  tributaries ;  for  the  amount 
of  sand,  gravel,  and  clay  which  had  been  dropped  by  the  ice 
was  immense,  and  it  lay  loose,  easy  to  be  taken  up  by  streams 
the  rains  might  make. 

The  Mississippi  Valley  was  the  outlet  for  the  waters  of  the 
great  region  it  now  drains ;  and  its  floods  during  the  whole 
Glacial  period  must  have  been  great,  and  floating  ice  laden 
with  northern  stones  must  have  often  been  hurried  off  down 
stream  to  the  Gulf.  During  the  melting  it  made  thick  deposits 
on  the  way  to  the  Gulf,  as  observed  by  Hilgard,  and  in  Mis- 
sissippi, bowlders  as  large  as  a  bushel  basket  are  found  in  the 
beds. 

In  Europe  and  Great  Britain  the  Champlain  period  was  one 
of  subsidence  over  the  higher  latitudes,  as  in  America,  and 
the  subsidence  was  greatest  to  the  north.  In  France  and  Bel- 
gium the  depression  below  the  present  level  was  ~>0  to  100 
feet ;  in  southern  England  100  to  200  feet.  In  Sweden  it  was 
200  at  the  south  to  400  or  500  to  the  northeast,  —  so  great  that 
an  ocean  channel  then  connected  the  Baltic  with  the  White 
Sea. 

Between  the  Champlain  and  Recent  periods,  Europe  passed 
through  a  second,  but  less  severe  Glacial  epoch.  Marks  of  it 
have  been  pointed  out  in  glacial  deposits  in  the  Alps  and  other 
places,  but  especially  in  southern  France,  through  the  occur- 


QUATERNARY    ERA.  265 

rence  in  great  quantities  of  remains  of  the  Reindeer,  a  cold- 
latitude  animal.  With  the  bones  of  the  Reindeer  there  are 
also  those  of  other  cold-climate  species.  This  epoch  is  called 
the  J'dndccr  epoch.  After  it  conies  the  Recent  period  in 
geological  history. 

LIFE  OF  THE  PLEISTOCENE,  OR  THE  GLACIAL  AND 
CHAMPLAIX  PERIODS. 

1.  General  Observations.  —  The  plants  and  the  lower  tribes 
of  the  Animal  kingdom  in  the  early  part  of  the  Quaternary 
were  essentially  the  same  as  now.  The  species  of  Corals 
making  coral-reefs  in  the  tropics  were  probably  in  exist- 
ence and  at  work  before  the  close  of  the  Tertiary  age; 
and  the  same  is  true  of  most  of  the  Invertebrates  of  the 
modern  world,  and  also  of  the  plants. 

There  must  have  been  some  exterminations  as  a  conse- 
cpiience  of  the  cold  of  the  Glacial  period,  and  of  the  ice 
of  high-latitude  regions.  Many  plants  were  driven  south 
by  the  coming  on  of  the  cold,  and  thus  escaped  destruc- 
tion; and  some  of  these  now  live  on  Mount  Washington 
and  other  high  summits  of  temperate  North  America.  Birds 
must  have  shortened  their  migrations  northward  and  length- 
ened them  southward,  and  for  the  most  part  they  may  have 
escaped  catastrophe.  The  beasts  of  prey,  cattle,  and  other 
large  Mammals  of  Drift  latitudes  must  i  also  to  a  great 
extent  have  moved  toward  the  tropics  as  the  rigors  of  the 
approaching  ice-period  began  to  be  felt.  Certain  it  is,  that 


266  CENOZ01C    TIME. 

after  the  ice  had  gone,  a  large  population  of  brute  Mam- 
mals moved  in  from  the  warm  southern  latitudes  over  Europe 
and  the  other  continents;  and  facts  seem  to  prove  that  they 
hung  about  the  southern  limit  of  the  ice,  and  often  moved 
northward  with  the  lulls  in  the  intensity  of  the  climate  or 
the  shortening  in  at  intervals  of  the  ice-field. 

2.  Brute  Mammals.  —  The  brute  Mammals  appear  to  have 
reached  their  maximum  in  numbers  and  size  during  the 
Avarm  Champlain  period.  Those  of  Europe,  Great  Britain, 
and  America  were  largely  warm-climate  species,  such  as  now 
are  confined  to  warm-temperate  and  tropical  regions.  Only 
in  a  warm  period  like  the  Champlain  could  they  have  there 
thrived  and  attained  their  gigantic  size.  The  great;  abun- 
dance of  the  remains  and  their  condition  show  that  the  cli- 
mate and  food  were  all  the  animals  could  have  desired. 
They  were  masters  of  their  own  wanderings  and  had  their 
choice  of  the  best.  But  the  colder  conditions  of  the  Kecent 
period  which  followed  were  less  favorable,  and  many  <>f  the 
species  are  now  extinct. 

Remains  of  these  Mammals  have  been  found  in  deposits 
along  the  margins  of  rivers  and  lakes;  in  marshes,  \vhere 
they  became  mired;  in  caves,  buried  in  the  stalagmite  (page 
40)  that  was  deposited  over  their  deserted  skeletons.  In 
Great  Britain  and  Europe  the  caves  were  the  ha i mis  of  Hears, 
Hyenas,  and  Lions,  much  larger  than  any  of  the  kinds  no\v 
living;  these  beasts  of  prey  dragged  into  their  caves  the  bodies 
of  the  animals  they  fed  upon.  The  Cave  Bear  resembled 


QUATERNARY    ERA. 


267 


much  the  Grizzly  Bear  of  western  North  America;  and  the 
('a  vi-  Hyena  and  Cave  Lion  are  regarded  as  the  same  in  spe- 
cies with  the  African  Hyena  and  Lion,  although  these  modern 
kinds  are  dwarfs  in  comparison. 

\Yith  these  there  were  in  Great  Britain  and  Europe  species  of 

FIG.  290. 


Skeleton  of  Mastodon  Americanus. 

Ehinoceros,  a  Hippopotamus,  the  Siberian  Elephant  or  Mam- 
moth, the  Brown  Bear,  Wolf,  Wild  Cat,  Lynx,  Leopard,  Fox, 
Elk,  Deer,  and  others.  The  modern  species  of  Horse  was 
among  them.  The  Irish  Deer  (Cervus  megaceros),  skele- 
tons of  which  have  been  found  in  Irish  bogs,  had  a  height 


268 


CENOZOIC    TIME. 


to  the  tip  of  the  antlers  of  10  to  11  feet,  and  the  span 
of  the  antlers  was  sometimes  12  feet.  The  Elephant  (Elu- 
phas  primiyenius)  and  the  most  common  Rhinoceros  (R.  {/<•//<>- 
rinus)  had  a  hairy  covering,  which  fitted  them  to  roam 
over  regions  in  the  far  north.  The  remains,  especially  those 
of  the  Elephant,  show  that  they  lived  in  great  herds  over 
northern  Siberia,  where  now  the  mean  temperature  of  the 

FIGS.  291,  292. 
291 


Teeth  of  Mastodon  and  Elephant. 
Fig.  291,  Mastodon  Americamis  ex.  J) ;  292,  Elephas  priiiiigviiius. 

year  is  5°  to  10°  F.  The  Rhinoceros  had  a  length  of  11| 
feet,  and  the  Elephant  was  nearly  a  third  taller  than  the 
largest  of  modern  Elephants. 

In  North  America  also  there  were  large  Lions  and  Bears, 
but  none  of  them,  so  far  as  known,  made  caves  their  dens. 
The  largest  of  the  species  was  the  Mastodon  (Fig.  290),  an 
animal  with  tusks  and  trunk  like  an  Elephant.  When  full 
grown  it  was  12  to  13  feet  in  height,  and  to  the  extremi- 
ties of  the  tusks  25  feet  long.  The  teeth  had  a  crown  as 
large  in  area  as  this  page,  and  of  the  form  shown  in  Fig. 


(.U-ATKUNAKV    ERA.  269 

L'lll.  Skeletons  have  been  found  in  marshes  where  the  heavy 
beasts  were  mired;  and  portions  of  their  undigested  food  — 
the  small  branches  of  spruces  and  other  trees  —  have  been 
taken  from  between  their  ribs,  where  the  stomach  was  once 
trying  to  digest  them. 

There  were  also  American  Elephants  of  great  size,  of  the 
same  species   as   the   Siberian.     Fig.   292  represents  a  tooth 

FIG.  it»3. 


Megatherium  Cuvieri  (  x 


of  one  found  in  Ohio;  it  is  a  little  larger  than  that  of  the 
Mastodon.  There  were  also  Horses  of  large  size,  Tapirs, 
Oxen,  Beavers,  and  various  gigantic  species  of  the  tribe  of 
Sloths. 

The  Sloth  tribe  was  especially  characteristic  of  South 
America.  The  modern  Sloth  is  as  large  as  a  dog  of  me- 
dium size.  The  species  of  the  Champlain  period  included  a 
J/^/^///^/-/"//rf  (Fig.  293),  which  was  larger  than  the  'largest 
of  existing  Rhinoceroses.  As  the  figure  shows,  it  was  a  lazy 


270  CENOZOIC   TIME. 

beast ;  the  bones  of  the  hind  legs  are  much  like  logs,  and  those 
of  the  fore  feet  are  furnished  with  hands  a  yard  long  for  pull- 
ing down  trees  after  the  animal  raised  itself  erect  for  the  pur- 
pose on  its  hind  legs  and  enormous  tail,  —  a  third  support. 
This  is  one  of  many  kinds  of  gigantic  Sloth-like  animals 
that  lived  in  South  America  during  the  era.  Other  related 
species  had  a  shell  somewhat  like  the  modern  Armadillo ;  and 
these  also  were  gigantic,  one  of  them  (Fig.  294)  measuring  5 
feet  across  its  shell,  and  having  a  length  of  at  least  9  feet. 

FIG.  294. 


Glyptodon  clavipes  (  x 


In  Australia  the  Mammals  are  now,  with  few  excep- 
tions, Marsupials,  the  Kangaroo  being  one  of  them.  They 
were  also  Marsupials  then;  but  the  ancient  kinds  partook 
of  the  peculiar  feature  of  the  era,  —  great  magnitude,  some 
of  the  species  being  as  large  as  a  Hippopotamus,  one  having 
a  skull  a  yard  long,  and  many  of  them  being  far  larger  than 
any  modern  Marsupial. 

Thus  the  brute  races  of  the  Middle  Quaternary  on  all 
the  continents  greatly  exceeded  the  modern  races  in  magni- 


QUATERNARY  ERA.  271 

tude.  Why  they  did  so,  no  one  has  explained,  beyond  saying 
that  the  climate  was  favorable  to  great  size. 

The  genial  climate  of  the  Champlaiii  period  was  abruptly 
terminated ;  for  carcasses  of  the  Siberian  Elephants  were 
frozen  so  suddenly  and  so  completely  at  the  change,  that 
the  flesh  has  remained  till  these  modern  times  untainted. 
Xear  the  close  of  the  last  century,  one  huge  carcass  dropped 
out  of  the  ice-cliff  at  the  mouth  of  the  Lena,  and  for  a 
while  made  food  for  dogs.  The  existence  of  a  hairy  cover- 
ing was  then  first  ascertained.  A  hairy  Rhinoceros  has 
also  been  found  in  the  ice.  This  change  of  climate  was 
probably  connected  with  the  commencing  of  the  Reindeer 
epoch,  closing  the  Champlain  period;  it  was  then  that  the 
Reindeer  and  some  other  species  migrated  to  southern  France, 
to  live  there  until  the  cold  epoch  had  passed.  The  remains  of 
the  Reindeer  are  accompanied  by  those  of  the  Cave  Bear, 
Cave  Hyena,  Rhinoceros,  Elephant,  and  other  Champlain  spe- 
cies, showing  that  ail  lived  together  there  at  that  time. 

3.  Man.  —  Man  was  in  existence  during  the  Champlain 
period;  and  probably  in  its  earlier  part  before  the  ice  had 
disappeared.  Relics,  indicating  that  he  was  a  contemporary 
of  the  gigantic  Champlain  Mammals,  occur  in  various  cav- 
erns and  in  river  and  lacustrine  deposits,  in  Great  Britain, 
Europe,  Syria,  and  in  other  regions. 

The  relics  of  Man  are  stone  implements,  such  as  arrow- 
heads, hatchets,  pestles,  and  stone  chips  made  in  the  manufac- 
ture of  the  implements;  beads,  shells,  and  other  materials 


272  CENOZOIC    TIME. 

having  upon  them  his  markings  and  carvings;  his  pottery; 
the  charcoal  left  from  his  tires;  the  Lones  of  animals 
broken  lengthwise  to  get  out  the  marrow;  his  own  bones, 
skulls,  and  skeletons. 

In  Europe  and  western  Asia  the  stone  implements  of  the 
earlier  part  of  what  is  sometimes  called  the  Stone  age  are 
of  rude  make  and  unpolished.  This  part  of  the  age  has 
been  called  the  Paleolithic  epoch  in  human  history,  or  that 
of  the  oldest  stone  implements,  —  the  word,  from  the  Greek, 
signifying  old  and  stone.  The  stone  implements  occur  along 
with  bones  of  the  Cave  Bear,  Cave  Hyena,  Mammoth,  lihi- 
noceros,  and  several  other  Champlain  species,  and  also  with 
the  bones  of  Man ;  and  these  human  relics  are  so  associated 
with  those  of  extinct  Mammals  that  there  is  no  reason  to 
doubt  that  they  were  contemporaries. 

Next  came  the  Reindeer  epoch.  Its  stone  implements  are 
unpolished,  but  better  made  than  those  of  the  preceding 
era.  Besides  these  there  are  examples  of  bones,  shells,  horn, 
and  stone  engraved  with  the  forms  of  animals;  others 
that  are  variously  carved,  or  made  into  spear-heads  and 
other  forms;  and  also  perfect  human  skeletons.  Fig.  295 
represents  a  drawing,  on  ivory,  of  the  hairy  Elephant;  it 
was  found  in  the  cave  of  La  Madelaine,  in  Perigord,  south- 
ern France,  and  shows  that  the  Elephant  was  well  known 
to  the  men  of  the  period.  These  human  relics  are  asso- 
ciated with  remains  of  the  same  Champlain  Mammals  that 
occur  in  the  earlier  deposits,  and  also  with  great  numbers 


QUATERNARY     ERA. 


273 


of   the    bones  of   the    Keindeer,   and    many  of   the  Aurochs, 
Elk,  Deer,  and  other  species  of  later  time. 

The  bones  and  skeletons  of  Man  of  the  Stone  age,  thus  far 
found,  in  no  case  indicate  a  race  much  inferior  to  the  lowest  of 


Elephas  primigenius;  engraved  on  ivory  (x  g). 

existing  races,  or  intermediate  between  Man  and  the  Man 
Apes,  —  the  species  among  the  brutes  which  approach  him 
most  nearly.  But  still  they  are  those  of  uncivilized  Man,  and 
in  part  of  Man  of  a  low  order  of  faculties. 

The  skull  of  Neanderthal  (a  part  of  the  valley  of  the  Diissel, 
near  Diisseldorf)  is  the  worst,  but  it  is  probably  not  older  than 
others  having  better  skulls  and  higher  foreheads.  The  capacity 
of  the  cranium  was  75  cubic  inches,  which  is  greater  than  in 
some  existing  men.  A  jaw-bone  of  low  type,  found  in  the 
oldest  Belgian  deposits,  had  little  height  and  great  thickness, 
as  if  for  powerful  use,  and  the  posterior  of  the  molar  teeth  was 
the  largest,  —  a  brutal  feature. 
DANA'S  GEOT,.  STORY  —  18 


274  CENOZOIC    TIME. 

The  human  skeletons  of  the  Reindeer  era  in  southern  France 
are  in  part  those  of  men  of  unusual  height,  —  5  feet  9  inches  to 
over  6  feet ;  and  the  skulls  are  large  and  well  shaped,  with 
the  foreheads  high  and  capacious.  They  are  of  better  size  and 
shape  than  many  of  the  Reindeer  era  in  Belgium,  which  are 
small  and  after  the  Laplander  type. 

One  of  the  most  perfect  was  found  in  the  stalagmite  that 
formed  the  floor  of  the  cave  of  Mentone,  near  the  borders  of 
France  and  Italy,  on  the  Mediterranean.  Eight  feet  above  it  in 
the  stalagmite  there  were  remains  of  the  extinct  Rhinoceros 
and  other  Champlain  species.  The  man  would  compare  well, 
if  we  may  judge  from  the  skeleton,  with  the  best  among 
civilized  races,  —  his  forehead  broad  and  high,  and  rising  with 
a  facial  angle  of  85°,  his  height  6  feet;  and  yet  he  was  a 
European  savage  of  the  Reindeer  epoch;  for  about  him  lay  liis 
flint  implements  and  weapons,  his  chaplet  of  stag's  canines, 
and  shells  that  he  had  gathered  for  food  or  ornament  from  the 
shores  near  by.  The  tibia  or  shin-bone  was  somewhat  flat- 
tened, a  peculiarity  often  observed  in  the  skeleton  of  the 
American  Indian. 

The  brain-cavity  of  a  skull  found  in  the  cave  of  Cro- 
Magnon,  in  southern  France,  had  a  capacity  of  97  cubic  inches, 
which  is  very  much  above  that  of  ordinary  Man,  and  nearly 
three  times  that  of  the  highest  Man  Ape. 

In  North  America  cases  of  the  occurrence  of  ancient  human 
bones  or  skeletons  in  Quaternary  deposits  are  not  so  well 
authenticated  as  those  in  Europe.  Admitting  the  facts  that 


QUATERNARY   ERA.  275 

have  been  published,  they  do  not  give  Man  greater  antiquity 
than  those  above  mentioned. 

No  case  of  the  presence  of  human  relics  in  deposits  of  the 
Tertiary  age  on  any  continent  is  yet  well  established.  Mr. 
W.  P>oyd  Dawkins,  an  excellent  British  geologist  and  original 
observer  in  this  department  of  the  science,  states,  in  his  recent 
work  on  Cave  Hunting  (1874),  that  the  evidence  obtained 
proves  that  "Man  lived  in  Germany  and  Britain  after  the 
maximum  Glacial  cold  had  passed  away,"  and  that  no  human 
remains  "  have  been  discovered  up  to  the  present  time  in 
any  part  of  Europe  which  can  be  referred  to  a  higher 
antiquity  than  the  Pleistocene  (Quaternary)  age." 

The  second  Glacial  or  Reindeer  epoch  in  Europe  (which 
there  is  reason  to  believe  produced  effects  also  in  North 
America)  appears  to  have  finally  brought  to  a  close  the  era 
of  giant  beasts,  leaving  the  world  for  Man. 

3.  Recent  Period.  —  The  Champlain  period  was  brought  to  a 
close  by  a  moderate  elevation  of  the  land  over  the  higher 
latitudes,  bringing  the  continent  up  to  its  present  level. 
This  elevation  placed  the  old  sea-beaches  of  the  Champlain 
period  at  their  present  level  high  above  the  sea,  that  is,  over 
500  feet  near  Montreal,  over  200  feet  on  the  coast  of  Maine, 
and  so  on,  the  height  of  the  shell  beaches  being  a  measure 
of  the  amount  of  elevation.  River-valleys,  after  the  rise, 
had  a  steeper  slope  than  in  the  Champlain  period,  and  hence 
their  flow  was  increased  in  rate.  They  consequently  went 
on  cutting  down  their  beds  through  the  Champlain  deposits 


276 


TIME. 


of  the  valley  to  a  lower  level ;  and  at  the  time  of  their  annual 
floods  they  wore  away  the  deposits  on  either  side  of  the 
channel,  making  thereby  an  alluvial  flat  or  flood-ground ;  for 
every  river  has  a  flood-ground  which  it  covers  in  its  times 
of  flood,  as  well  as  a  channel  for  dry  times. 

This  sinking  of  the  river-beds  left  the  old  flood-grounds  as  a 
high  terrace  far  above  the  level  of  the  stream ;  and  the  great 

FIG.  296. 


Terraces  on  the  Connecticut  River,  south  of  Hanover,  N.  H. 

elevated  plains  still  remain  to  attest  the  vastness  of  the 
floods  from  the  melting  glacier.  In  the  course  of  the  elevation 
a  series  of  terraces  was  often  ma.dc1  along  the  valleys,  as 
illustrated  in  Fig.  296.  A  section  of  a  valley  thus  terraced  is 
represented  in  Fig.  297.  The  formation  terraced  is.  as  is 
shown,  the  Champlain;  in  the  (Jhaniplain  period  it  tilled, 


QUATKUNAUY    ERA.  277 

* 

in  general,  the  valley  across  (from /to/'),  excepting  a  narrow 
channel  for  the  stream,  the  whole  breadth  having  been  the 
flood-ground  of  the  Chaniplain  River.  But  after  the  elevation 
of  the  land  that  closed  the  Chaniplain  period  began,  the  river 
commenced  to  cut  down  through  the  formation,  making  one 
or  more  terraces  in  it,  on  either  side  of  the  stream.  In  Fig. 
297,  R  is  the  position  of  the  river-channel  after  the  terracing ; 


Section  of  a  Valley  with  its  Terraces  Completed. 

and  on  either  side  of  it  there  are  terraces  at  the  levels//',  dd', 
bb'j  and  also  another  on  the  right  side,  at  cV.  These  terrace- 
plains  are  usually  the  sites  of  villages.  They  add  greatly  to 
the  beauty  of  the  scenery  along  water  coiu-ses.  The  terraces 
usually  fail  where  the  valley  is  narrow  and  rocky. 

Hock-making  has  not  yet  ceased,  for  the  old  agencies — the 
waters,  the  winds,  and  life  —  are  still  at  work  with  unimpaired 
energies.  Sand-beds,  pebble-beds,  and  mud-beds  are  accu- 
mulating along  seashores  and  in  shallow  waters,  precisely 
like  those  that  were  hardened  into  ancient  sandstones,  con- 
glomerates, and  shales;  and  limestones  are  forming  from 
shells  and  corals  similar  to  ancient  limestones. 

Further  changes  of  level  are  still  going  on.  A  large  part 
of  Sweden  is  rising  at  the  slow  rate  of  four  feet  or  so  a  century, 


278  CENOZOIC    TIME. 

and  as  slowly  a  portion  of  Greenland  is  subsiding.  The  Atlantic 
coast  from  New  Jersey  to  Labrador  is  supposed  to  be  sinking, 
and,  along  New  Jersey,  at  the  rate  of  two  feet  a  century. 

Man,  in  the  Recent  period,  passed  the  last  part  of  his 
Stone  age,  styled  the  Neolithic  epoch.  In  Europe,  the  stone 
implements  of  the  epoch  include  polished  implements,  as  well 
as  those  which  are  merely  chipped ;  and  the  animal  remains 
found  in  the  same  beds  are  portions  of  skeletons  of  the  domes- 
tic Dog  and  other  existing  quadrupeds,  with  much  broken 
pottery.  The  epoch  is  called  the  Neolithic,  from  the  Greek  for 
new  and  stone.  The  shell-heaps  or  Kitchenmiddens,  of  the 
Danish  Isles  in  the  Baltic,  are  part  of  the  Neolithic  localities. 
Among  the  North  American  Indians,  the  Stone  age  was  con- 
tinued to  within  a  century  or  two. 

Besides  human  remains,  modern  fossils  include  corals,  shells, 
and  relics  of  all  the  various  tribes  of  the  passing  period. 

Moreover,  species  are  becoming  extinct ;  at  least  through 
Man,  if  not  in  other  ways.  The  Dodo,  an  extinct  bird  of  50 
pounds'  weight  (Fig.  298),  was  living  on  Mauritius  in  the 
seventeenth  century.  The  Moa,  larger  than  an  Ostrich,  and 
other  birds  with  it,  have  recently  disappeared  from  New 
Zealand.  The  Aurochs  (Bison  priscus)  of  Europe  is  nearly 
extinct.  Thus  wild  animals  have  begun  to  disappear  before 
advancing  Man.  The  same  is  true  of  plants. 

The  age  of  Man  now  has  as  its  fossils,  not  only  flint  imple- 
ments and  human  bones,  but  also  buried  cities,  temples,  statues, 
and  manuscripts. 


QUATERNARY   ERA. 


279 


FIG.  298. 


Extinct  Species.     Dodo,    with  the    Solitaire   and   an   Extinct   Species    of   Night 

Heron   in   Outline. 
From  -A  painting,  at  Vienna,  iiiruli-  by  Kohiml  Savery,  in  1628, 


280  GEOLOGICAL    HISTORY. 

The  system  of  life,  long  in  progress,  finally  reached  its  com- 
pletion in  a  being  that  could  search  into  the  earth's  history, 
study  Nature's  laws  and  investigate  the  system  of  the  universe ; 
and  who  has  thus  the  highest  credentials  of  kinship  Avith  the 
Infinite  Author  of  physical  and  moral  law.  The  progress  now 
of  chief  interest  is  no  longer  the  development  of  animal  races 
and  characters,  but  the  exaltation  of  Man  in  the  direction  of 
his  higher  nature. 


V.    OBSERVATIONS   OX   GEOLOGICAL   HISTORY. 
1.   Length  of  Geological  Time. 

To  the  question,  "  what  is  the  length  of  geological  time  ?  " 
geology  gives  no  definite  reply.  It  establishes  only  the  gen- 
eral proposition  that  time  in  lomj. 

The  Canon  of  the  Colorado  (page  103)  is  a  gorge  -00 
miles  long,  bounded  the  most  of  the  way  by  steep  walls 
of  rock  3000  to  5000  feet  in  height,  cut  through  sandstones, 
limestones,  and  other  rocks ;  and  at  bottom  over  parts  of  it, 
for  several  hundred  feet,  into  granite ;  and  above  the  lofty 
walls  a  few  miles  back  from  the  stream  the  pile  of  nearly  hori- 
zontal strata  is  continued  in  mountains  of  nearly  horizontal 
strata  to  a  height  of  7000  to  8500  feet  above  the  bed  of  the 
river.  All  the  facts,  as  its  describers  testify,  point  to  running 
water  as  the  agent  that  made  the  great  channel.  The  region 
was  imder  the  sea  until  the  close  of  the  Cretaceous  period,  for 


LENGTH    OF    GEOLOGICAL   TIME.  281 

marine  Cretaceous  strata  are  the  uppermost  rocks.  It  follows, 
then,  that  all  this  extensive  excavation  was  accomplished  by 
slow-acting  water  during  Cenozoic  time.  Surely  Cenozoic  time 
was  very  long. 

The  gorge  of  the  Niagara  River  below  the  Falls  has  a  length 
of  seven  miles.  It  is  the  work  of  the  waters  since  the  latter 
part  of  the  Glacial  period;  for  during  this  period  the  older 
channel  was  filled  up  by  deposits  of  drift  from  the  ice.  The 
water  has  consequently  made  this  excavation,  seven  miles  long, 
since  the  ice  left  the  region.  From  estimates  of  the  present 
rate  of  erosion,  the  length  of  the  time  of  erosion  is  between 
6000  and  7000  years. 

The  thickness  of  a  sedimentary  deposit  is  no  satisfactory 
basis  for  determining  the  length  of  time  it  took  to  form.  In 
a  sea  100  feet  deep,  100  feet  of  sediment  may  accumulate  ;  and 
the  thickness  could  not  exceed  this  (except  a  little  through 
wave-action  and  the  winds)  if  a  million  of  years  were  given  to 
the  work. 

Let  the  same  region  be  undergoing  a  subsidence  of  an  inch 
a  century,  and  the  thickness  might  increase  at  that  rate  ;  and 
much  faster,  if  a  yard  a  century  ;  and  with  either  rate,  giving 
time  enough,  any  thickness  might  be  attained.  Hence  a  stra- 
tum of  sandstone  100  feet  thick  may  have  been  formed  in  a 
thousandth  part  of  the  time  of  a  thin  intervening  bed  of  shale. 

Neverthefess,  the  aggregate  maximum  thickness  which  the 
strata  attained  during  the  several  ages  may  be  vised  for  an 
approximate  estimate  of  the  comparative  lengths  of  those  ages. 


282  GEOLOGICAL   HISTORY. 

On  such  data,  it  is  deduced  that  the  time  ratio  for  Paleozoic, 
Mesozoic,  and  Cenozoic  time  was  not  far  from  12  :  3  :  1.  Con- 
sequently, if  we  suppose  the  length  of  time  since  the  Paleozoic 
began  to  be  16  millions  of  years,  Paleozoic  time  will  include  12 
millions,  Mesozoic  3  millions,  and  Cenozoic  1  million.  Most  geol- 
ogists Avould  make  the  whole  interval  several  times  16  millions. 

2.    Progress  in  Development  of  the  Earth's  Features. 

The  earth  through  the  ages  made  progress :  — 

1.  In  its  Surface  Features :   from  the  condition  of  a  melted 
sphere  as  featureless  as  a  germ,  to  that  of  an  almost  univer- 
sal ocean  with  small  lands,  —  enough   of   land  to   mark  out 
the   feature-lines  of    the   future    continents;    and   at   last  — 
after    slow    expansion    southward,    a    lifting    of    mountain 
ranges  at  long  intervals,  and  a  retreating  of  the  waters  —  to 
the  existence  of  great  continents  having  high  mountain  bor- 
ders and  well-watered  interior  plains. 

2.  In  its  River-systems :    from  the  existence  of  only  little 
streamlets  draining  small  lands  in  the  Archaean  and  Silurian 
eras,  and  making  no   permanent   geological   record  beyond  a 
rain-drop    impression,    to    a   condition    of    vast    freshwater 
lakes   and   marshes   when   beds   of   vegetable   material  accu- 
mulated  for  the   making  of  coal-beds ;    and  finally  to   that 
of  the   completed   continent,   when   a  single  river  (with   its 
tributaries)  drains,  waters,  and  contributes  ferity  to  hun- 
dreds of  thousands  of  square  miles  of  surface,  and  the  work 
of  fresh  waters  in  rock-making  exceeds  that  of  the  ocean. 


BEGINNING    AND    END    OF   THE    EARTH.  283 

3.  In  its  Climate:  from  a  condition  of  general  uniformity 
of  temperature,  to,  at  last  (though  with  interrupted  prog- 
ress) that  of  the  present  diversity,  when  the  polar  regions 
have  a  permanent  capping  of  ice,  and  only  the  equatorial 
regions  perpetual  verdure. 

•4.  In  its  Living  Adornments:  from  an  era  when  the  small 
rocky  lands  were  bare,  or  gray  and  drear  with  lichens, 
and  all  other  life  was  of  the  simplest  kind  and  below 
the  water  level,  to  a  time  of  flowerless  forests  and 
jungles  over  immense  plains,  yet  with  no  sound  from  living 
Nature  more  musical  than  the  Amphibian's  croak;  and  on- 
ward to  the  better  time  when  the  earth  abounds  in  flowers 
and  fruits  and  birds,  and  is  covered  with  the  homes  of  Man. 

3.    The  System  of   Nature  of  the  Earth   had  a  Beginning  and 
will   have   an   End. 

A  system  of  progress  or  development  in  the  earth  as  much 
implies  that  it  had  a  beginning,  as  that  in  any  plant  or  ani- 
mal. Man,  Mammals,  Fishes,  Mollusks,  Khizopods,  Plants, 
all  had,  according  to  geological  history,  their  beginning;  so 
also  mountains,  valleys,  rivers,  continents,  rocks;  and  so 
also  the  earth;  and  therefore  the  system  of  nature,  whose 
development  went  forward  in  and  through  it,  had  its  begin- 
ning. 

If  this  is^rue  of  one  sphere  in  space,  we  may  rightly  take 
another  step  and  assert  that  the  universe  had  its  beginning. 

It  also  admits  of  demonstration  that  the  earth  will  have 


284  GEOLOGICAL    HISTORY. 

its  end.  A  finished  state  is  always  the  state  before  decline 
and  death.  The  earth  is  dependent  for  all  the  beauty  in 
its  living  adornments,  and  even  for  the  existence  of  its  life, 
on  the  heat  and  light  of  the  sun.  The  sun  is  annually  losing 
its  heat;  and  however  infinitesimal  the  amount  of  loss,  it  is 
sure  to  end  in  a  cooled  and  dark  sun;  and  hence,  even  long 
before  the  sun  is  cold,  the  earth,  supposing  it  to  have  met 
with  no  earlier  catastrophe,  will  have  become  dark  and  life 
less,  literally  a  dead  earth. 

4.    Progress  in  Life. 

1.  From  the  Simple  to  the  Complex.  —  The   progress  in  life 
was  in  general  from  the  simpler  forms  to  the  more  complex, 
or  from  the  low  to  the  high.     This  truth  has  been  illustrated 
in   each   chapter   of  the  preceding  geological  history. 

2.  By  Gradual  Steps.  —  Species  appeared  and   disappeared, 
not  only  at  the   beginning   of   ages,  or   of  the  subdivisions 
of  ages  called  periods,  but  also  during  the  progress  of  periods, 
each  of  the   successive   strata    containing    some   fossils    not 
found    below,   and   failing   of    others   that   are   abundant  in 
underlying  beds.     There  were  at  times  epochs  of  wide-spread 
catastrophe,  ending  periods ;  and  two  of  them,  those  closing 
Paleozoic  and  Mesozoic  time,  were  nearly  or  quite  universal 
for    the   Continental   seas.      But    these    must   have  left  iin- 
harmed   the    life  of    the   deep   ocean;    and   they    could   not 
have    exterminated    all    the    life   of    the    emerged   land,  or 
even  of  the  whole  area  of  Continental  seas. 


PROGRESS    IN     LIFE.  285 

3.  According  to  System. — The  first   animal  life  was  prob- 
ably    the     Protozoan,     or     Rhizopods,     Radiolarians,     and 
the     like, — -kinds     that     are     minute     and     destitute     of 
members.       But    later,    the    grander    divisions     of    animals 
were    defined;    and    the    species    which    appeared    afterward 
in   the   long   succession   were   constructed    according    to   one 
or     another     of     the     systems     of     structure     thus     estab- 
lished.    Each  division  became  displayed  in  higher  and  more 
diversified  forms   by  the   new   species  that   came  into  exist- 
ence as  time  moved  on.     The  first  of  the  Vertebrates  were 
the  Fishes,  —  the  simplest  of  the  principal  Vertebrate  classes. 
Even  in  these  aquatic  species  the  arms  and  legs  of  the  higher 
Vertebrates  were  present,  though  only  in  the  state  of   fins  ; 
and  the  lung,  though  only  as  a  cellular  air-bladder;  and   the 
ear,  though  only  as  a  closed  cavity  containing  a  loose  bone; 
and  so   with   other  parts.     Thus   the  earliest  of  Vertebrates 
possessed   in   an    incipient   stage   many   of    the   organs   that 
became    fully    developed    in    the    later    and    higher    Verte- 
brates.    And   in   the   succession  of  species   that   existed,  all 
were  made   on  the  fish-structure  as   its  basis,  even  the  spe- 
cies of  the  highest  class,  —  those  of  Mammals  and  Man.     A 
zoologist,  in   order  to  understand  the  fundamental  elements 
in  the  human   structure,  goes   to   the   fish   and  the  frog  for 
instruction;  and  Nature  is  so  true  to  her  fundamental  prin- 
ciples, that  he  finds  there  what  he  looks  for. 

4.  A   System   of   Development   or    Evolution.  —  With    every 
step  there  was  an  unfolding  of   a  plan,   and   not   merely  an 


286  GEOLOGICAL    HISTORY. 

adaptation  to  external  conditions.  There  was  a  working 
forward  according  to  preestablished  methods  and  lines  up 
to  the  final  species,  Man,  and  according  to  an  order  so 
perfect  and  so  harmonious  in  its  parts,  that  the  progress 
is  rightly  pronounced  a  development  or  evolution.  Creation 
by  a  divine  method,  that  is,  by  the  creative  acts  of  a  Being  of 
infinite  wisdom,  whether  through  one  fiat  or  many,  could  be  no 
other  than  perfect  in  system,  and  exact  in  its  relations  to 
all  external  conditions,  —  no  other,  indeed,  than  the  very 
system  of  evolution  that  geological  history  makes  known. 

5.  Culmination  and  Decline  of  Tribes.  —  As  has  been  brought 
out  in  the  history,  Trilobites,  Brachiopods,  and  Crinoids, 
besides  other  groups  of  Animals,  reached  their  maximum, 
or  culminated,  in  Paleozoic  time;  Amphibians,  in  the  first 
period  of  the  Mesozoic  era;  Reptiles  among  Vertebrates, 
and  Cephalopods,  the  highest  of  Mollusks,  in  the  later 
Mesozoic;  brute  Mammals,  in  the  Cham  plain  period  of 
Cenozoic  time.  So,  again,  in  the  kingdom  of  plants, 
the  highest  Cryptogams  —  the  Acrogens  —  culminated  in  the 
Carboniferous  period;  Cycads,  in  the  middle  Mesozoic;  while 
Palms  and  Angiosperms  have  the  present  era  as  their  time 
of  greatest  display  and  perfection.  These  are  a  few  exam- 
ples, showing  that  progress  did  not  go  on  regularly  upward; 
but  that  the  old,  not  only  in  species,  but  also  in  tribes  and 
orders,  were  culminating  and  then  passing  away,  as  new  and 
higher  tribes  were  introduced,  in  the  progressing  evolution 
of  the  kingdoms  of  life. 


PROGRESS    IN    LIFE.  287 

6.  Parallelism  between  the  Progress  of  the  System  of  Life  and 
the  Progress  of  Individual  Life.  —  An  animal,  in  its  growth  from 
the  germ  —  or,  as  it  is  called,  its  embryonic  development  — 
passes  through  a  succession  of  forms  before  reaching  the  adult 
state.  In  Mammals  the  changes  after  birth  are  small,  the 
larger  part  of  them  having  taken  place  before  birth.  But  in 
the  lower  animals  the  successive  forms  a?e  often  widely  di- 
verse, and  they  frequently  mark  successive  stages  in  the  life 
of  the  animal.  Thus,  in  Insects,  there  is  the  caterpillar  or 
grub  stage  before  the  adult ;  and  in  many  Crustaceans,  Mol- 
lusks,  Worms,  and  Radiates  there  are  several  such  stages. 

Now  species  have  existed,  and  many  now  exist,  which 
have  the  general  characters  of  the  forms  in  these  lower  stages  j 
and,  in  accordance  with  the  above  proposition,  the  order  of 
their  appearance  in  the  geological  series  is,  in  general,  as  an- 
nounced by  Agassiz,  that  of  their  development  in  the  embry- 
onic series.  Thus,  as  the  worm-like  grub  precedes  the  adult 
Insect,  so  Worms,  in  geological  history,  preceded  Insects.  As  a 
fish-like  condition  of  an  Amphibian  precedes  the  adult  form  in 
which  the  fish-like  features  are  lost,  so  Fishes  preceded  Am- 
phibians. The  examples  of  the  principle  are  numerous.  Some 
authors  have  so  great  faith  in  it,  that  they  are  ready  to  decide 
as  to  the  form  of  the  earliest  species  of  a  tribe  from  the  earlier 
stages  in  individual  development.  But  this  is  unsafe,  since 
such  forms  may  have  come  late  into  the  system  of  life  as  well 
as  early;  inasmuch  as  progress  was  not  in  all  cases  upward 
progress. 


288  GEOLOGICAL    HISTORY. 

\Yhere  the  parallelism  above  mentioned  is  not  apparent  in 
the  general  form  or  structure,  it  is  still  manifested  in  certain 
comprehensive  laws  common  to  both  kinds  of  progress,  the  geo- 
logical and  embryonic.  The  following  are  some  of  these  laws : 

1.  The  low  before  the  relatively  hiijh. 

2.  *  Tlie  simple  before  the  complex.      A  germ  has  little  dis- 
tinction of  parts ;  the  animal  it  is  to  evolve  is  there  in  a  very 
general  condition;  that  is,  without  any  special  organs.     As  de- 
velopment of  a  Mammal  goes  on,  the  defining  of  the  head  be- 
gins, and  this  is  one  of  the  first  steps  in  the  evolving  of  special 
parts,  or  in  the  specialization  of  the  structure.      Protuberances 
also  form  and  commence  the  defining  of  the  limbs ;  and  then 
finally,  the  parts  of  the  limb  become  distinct,  or  are  specialized. 
Thus  it  is  throughout  the  structure,  until  the  specialization  of 
the  parts  peculiar  to  the  particular  animal  is  completed. 

This  law  of  the  general  before  the  sjieo'ul  is  a  law  also  in  the 
geological  progress  of  the  system  of  life.  In  a  Fish,  the  earliest 
of  Vertebrates,  the  vertebrate  structure  is  exhibited  in  a  very 
generalized  condition.  The  vertebral  column  consists  of  one 
single  uniform  range  of  vertebrae  without  a  neck  portion,  and 
without  a  pelvis  to  divide  the  body  from  a  tail  and  afford 
support  to  hind  limbs ;  the  limbs  are  fins,  and  hence  only  rudi- 
ments of  limbs;  the  vertebrae  have  great  simplicity  of  form; 
the  teeth  are  all  of  the  simplest  kind ;  the  lung  is  merely  an 
air-bladder,  and  so  on.  Thus,  all  through  the  structure,  a  Fish 
is  an  exhibition  of  the  vertebrate  type  in  a  generalized  state. 
The  Vertebrates  which  succeeded  to  Fishes  —  the  Amphibians 


PROGRESS   IN   LIFE.  289 

— have  the  grand  divisions  of  the  body  well  brought  out,  and  are 
specialized  also  as  to  limbs  even  to  the  toes,  and  in  other  ways. 
Passing  onward  in  time,  the  new  Vertebrates  appearing  exhib- 
ited successively  a  more  and  more  complete  specialization  of 
organs  and  functions  up  to  Man. 

This  law  of  progress  from  simple  to  complex  has  its  excep- 
tions; for  Snakes,  which  are  limbless,  succeeded  to  higher 
Keptiles  which  had  limbs.  But  such  cases  only  exemplify 
another  fact,  already  illustrated, — that,  while  upward  progress 
was  the  rule,  there  was  also  progress  downward,  and  especially 
after  the  time  of  culmination  of  a  tribe  had  passed. 

3.  Stationary  forms  sometimes  before  the  locomotive.  Thus, 
Crinoids,  part  of  the  earliest  life  of  the  globe,  were  sta- 
tionary species  living  attached  by  a  stem;  and,  after  these, 
there  were  free  Asterioids.  So  the  young  of  the  modern  Cri- 
noid  has  a  stem-  for  attachment,  and  loses  it,  in  many  species, 
as  it  becomes  an  adult  (a  Comatulid). 

7.  Origin  of  Man.  —  The  interval  between  the  Monkey  and 
Man  is  one  of  the  greatest.  The  capacity  of  the  brain  in 
the  lowest  of  men  is  68  cubic  inches,  while  that  in  the  highest 
Man  Ape  is  but  34.  Man  is  erect  in  posture,  and  has  this 
erectness  marked  in  the  form  and  position  of  all  his  bones, 
while  the  Man  Ape  has  his  inclined  posture  forced  on  him 
by  every  bone  of  his  skeleton.  The  highest  of  Man  Apes 
cannot  walk,  except  for  a  few  steps,  without  holding  on  by 
his  fore  limbs ;  and,  instead  of  having  a  double  curvature  in 
his  back  like  Man,  which  well-balanced  erectness  requires,  he 
DANA'S  GEOL.  STORY  —  19 


290  GEOLOGICAL  HISTORY. 

has  but  one.  The  connecting  links  between  Man  and  any 
Man  Ape  of  past  geological  time  have  not  been  found,  although 
earnestly  looked  for.  No  specimen  of  the  Stone  age  that  has 
yet  been  discovered  is  inferior,  as  already  remarked,  to  the 
lowest  of  existing  men;  and  none  is  intermediate  in  essential 
characters  between  Man  and  the  Man  Ape. 

The  present  teaching  of  geology  very  strongly  confirms  the 
belief  that  Man  is  not  of  Nature's  making.  Independently 
of  such  evidence,  Man's  high  reason,  his  unsatisfied  aspira- 
tions, his  free  will,  all  afford  the  fullest  assurance  that  he 
owes  his  existence  to  the  special  act  of  the  Infinite  Being 
whose  image  he  bears. 

8.  Man  the  Highest  Species. — It  is  sometimes  queried 
whether  the  future  may  not  have  its  various  new  species  of 
life,  and,  among  them,  some  higher  than  existing  Man ;  whether 
the  era  now  passing  is  not  to  be  followed,  as  was  true  of  the 
Carbonic,  or  the  Reptilian,  by  another  still  more  glorious  in  its 
living  species ;  whether,  if  one  of  the  great  Dinosaurs  of  the 
Mesozoic  age  could  have  thought  about  his  own  and  other 
times,  he  would  not  have  imagined  his  era  the  last  and  the 
best  possible ;  and  whether  Man  is  not  playing  as  foolish  a  part 
in  styling  himself  the  "  lord  of  creation." 

Against  the  introduction  of  new  species  in  coming  time 
science  has  little  to  urge.  But  there  is  strong  reason  for  hold- 
ing that,  whatever  the  changes  in  the  lower  tribes,  existing 
Man  will  always  remain  the  highest  in  the  series. 

(1)    Science  has  made  known  that  the  highest  of  species 


PROGRESS  IN  LIFE.  291 

next  to  Man,  that  is,  the  brute  Mammals,  have  already  passed 
their  maximum  (page  266) ;  hence,  the  rest  of  time  remains 
for  the  culmination  of  the  only  higher  type,  that  of  Man. 
And,  as  this  type  includes  now  but  one  species,  we  have  rea- 
son for  expecting  no  new  species  in  the  future. 

(2)  From  geological  history  we  learn   also  that  the  type 
of  Vertebrates  commenced  in  kinds  that  were  horizontal  in 
attitude,  —  the   Fishes;   and  that   from  the  horizontal   there 
was,  in   the   Reptiles   and  Mammals,  a   raising  of  the  head 
above   the   line  of  the  body,  up   to  the  Ape,  in  which  the 
attitude  is  nearly  vertical;   and,  finally,  to  perfect  verticality 
in  Man,  a  being  having   the  head  placed  directly  over  the 
body  and  hind  limbs.     Thus,  as  Agassiz  observed,  the  last 
term   in  the   series   of    Mammals   has   been   reached;    there 
can  be    nothing   beyond.      This    is   true    as    to  the   general 
type  of  structure ;  but  it  leaves  it  an  open  question  whether 
there  may  not  be  another  species  of  Man,  or  erect  beings, 
of  still  higher  grade. 

(3)  But  a  different  species   of  Man   higher  than  existing 
Man  is  not  a  possibility.     We  can  conceive  of  other  species 
of  Man  distinguished  by  having  some  of  the  external  fea- 
tures of  the  Man  Apes.     But  these  are  marks  of  inferiority, 
and,  if  possible  in   a  type  of   so   high  grade,  could  belong 
only  to  inferior  species. 

The  increasing  erectness  and  breadth  of  forehead  in  Man, 
and  the  shortening  of  the  jaws,  giving  a  nearly  vertical 
line  to  the  front,  which  are  a  known  result  of  culture,  indi- 


292  GEOLOGICAL   HISTORY. 

cate  the  course  which  upward  progress  must  take.  And  in 
these  points  and  some  others  closely  related,  the  limits  of 
perfection  have  been  nearly  reached  by  some  among  the 
present  race.  Further  improvement  can  give  physically  only 
larger  capacity  to  the  brain  and  greater  beauty  of  form  to 
the  whole  structure,  and  make  these  qualities  more  general. 
No  wide  divergence  from  existing  Man  can  be  conceived 
of.  When  all  possible  change  in  these  directions  has  been 
accomplished,  Man  will  still  be  Man,  and  no  more  the  head 
of  the  system  of  life  than  he  is  at  present. 

(4)  Beyond  all  this  we  may  say,  that  since  no  other 
species  but  Man  has  ever  been  capable  of  reviewing  the 
past  or  contemplating  the  future;  and  since  Man  not  only 
has  all  time  and  all  Nature  within  the  range  of  his  thoiight 
and  study,  but  can  even  yoke  Nature  for  service,  and  in 
fact  has  her  already  at  work  for  him  in  numberless  ways, 
the  system  with  such  a  head  must  be  complete. 

Nature,  through  Man,  has  attained  to  the  possession  of  a 
living  soul  capable  of  putting  her  once  wasted  energies  into 
strong  and  combined  movement  for  social,  intellectual,  and 
moral  purposes,  and  this  is  the  consummation  that  the  past 
has  ever  had  in  prospect. 

The  Man  of  the  future  is  Man  triumphant  over  dying 
Nature,  exulting  in  the  freedom  and  privileges  of  spiritual 
life. 


INDEX. 


ACONCAGUA,  87. 

Acrogens,  Carboniferous,  191. 

Devonian,  173. 

era  of.  134,  145,  184. 

Lower  Silurian,  154. 

Upper  Silurian,  167. 
Acrotreta,  149. 
Actinocyclus,  52. 
Actinolite,  21. 
Actinoptychus,  51,  52. 
Adirondacks,  138. 
Agate,  18. 
Albite,  20. 

Algie.    See  SEAWEEDS. 
Alleghany  Mountains,  making  of,  114,  208. 
Alluvial  deposits,  67. 
Alps,  elevation  of,  247. 

Glacial  period  in,  259. 

glaciers  in,  79. 
Alumina,  19. 
Aluminum,  14. 
Amethyst,  17. 
Ammonites,  217,  231. 
Ammonoids,  177,  216,  229,  281. 
Amphibians,  133. 

Carbonic,  197. 

era  of,  125,  134,  145,  184. 

Triassic  and  Jurassic,  218,  220. 
Amygdaloid,  34. 
Anchisaurus,  221. 
Andes,  elevation  of,  235. 
Angiosperms,  Cretaceous,  229. 

Tertiary,  242. 

Animal  kingdom,  classification  of,  125. 
Anisopus,  219. 
Anomospus,  219. 
Anthracite,  189. 
Anticline,  110. 

Appalachian  Mountain  chain,  118. 
Appalachian  Mountain  system,  207. 
Appalachian  region,  folded  rocks  of,  110,  204. 

thickness  of  formations  in,  208. 
Appalachians,  making  of,  114,  203. 
Archaean  time,  125,  187. 
Archseocalamites,  174. 
Archaeocyathus,  148. 


Arenig  series,  154. 
Arequipa,  86.  • 

Argillaceous  sandstone,  31. 
Argillyte,  81. 
Aristozoe,  150. 
Armadillos,  Quaternary,  270. 
Arsenic,  14. 
Arthrolycosa,  196. 
Articulates,  131. 

Cambrian,  149,  151. 

Carboniferous,  195. 

Devonian,  176,  178. 

Lower  Silurian,  158. 

Upper  Silurian,  168. 
Asaphus,  158. 
Asterophyllites,  174. 
Astraea,  44,  45. 
Athyris,  127. 

Atmosphere,  agency  of,  58. 
Atolls,  78. 
Atrypa,  127. 
Augite,  21,  22. 
Aurochs,  278. 
Avicula,  129. 
Aymestry  limestone,  167. 
Azoic.    See  ARCHAEAN. 
Azurite,  29. 

BACILLARIA,  51. 

Bala  beds,  154. 

Barite,  25. 

Barium  sulphate,  25. 

Barrier  reefs,  74. 

Basalt,  33. 

Basaltic  columns,  37. 

Base-level,  68. 

Bear,  cave,  266. 

Beetles,  Carboniferous,  195. 

Belemnitella,  232. 

Belemnites,  218,  231. 

Billingsella,  149. 

Biotite,  21. 

Birds,  133. 

Cretaceous,  232. 

Jurassic,  218,  224. 

Tertiary,  244, 


293 


294 


INDEX. 


Bison  prisons,  278. 
Bituminous  coal,  189. 
Black  lead.    See  GRAPHITE. 
Blue  Eidge,  188. 
Bog  iron  ore,  27. 
Bowlder  clay,  259. 
Bowlders,  250. 
Brachiopods,  127. 

Cambrian,  148,  151. 

Carbonic,  187,  195. 

Devonian,  176. 

Lower  Silurian,  157. 

Upper  Silurian,  168,  169. 
Brines  of  Salina,  166. 
Bryozoans,  127, 128. 

Lower  Silurian,  157. 

Tipper  Silurian,  168. 
Buthotrephis,  155. 

CAIRNGORM  stone,  17. 
Calamary,  130. 
Calamites,  174,  194. 
Calcareous,  rocks,  29,  48. 

skeletons  of  animals  and  plants,  43. 

tufa,  40. 

Calciferous  sandstone,  153. 
Calcite,  28. 
Calcium,  14. 
Calcium  carbonate,  23. 

action  of,  in  solidification  of  rocks,  92. 
Calcium  sulphate,  25. 
Calymene,  158. 
Cambrian  era,  125,  145. 
Camels,  Tertiary,  245,  246. 
Canadian  period,  153. 
Cannel  coal,  189. 
Carbon,  14. 

dioxide,  23. 
Carbonates,  28. 

Carbonic  acid.    See  CARBON  DIOXIDE. 
Carbonic  era,  125,  145,  184. 

changes  of  level  during,  198. 
Carboniferous  period,  187. 
Carcharodon,  243. 
Carcharopsis,  197. 
Catskill  Mountains,  106. 
Catskill  sandstone,  172. 
Caulopteris,  178. 
Cave  animals  of  Quaternary,  266. 
Cenozoic  time,  125,  287. 
Centipedes.    See  MYRIAPODS. 
Cephalaspis,  182. 
Cephalopods,  180. 

Cambrian,  151. 

Cretaceous,  281. 

Devonian,  177. 

Lower  Silurian,  157. 

Triassic  and  Jurassic,  215. 


Cervus  megaceros,  267. 

Cestracion,  179. 

Chain  coral,  169. 

Chalcopyrite,  28. 

Chalk,  29,  50,  228. 

Champlain,  Lake,  in  the  Quaternary,  263. 

Champlain  period,  250,  262. 

subsidence  in,  263. 
Chazy  limestone,  153, 
Chelonians.    See  TURTLES. 
Chemical  work  of  air  and  moisture,  58. 
Chemung  beds,  172. 
Chlorite,  23. 
Chrysalidina,  48,  230. 
Chrysolite.  23. 
Circumdenudation,  106. 
Clam,  242. 
Clay,  30. 

slate,  31. 
Cleavage,  15. 
Climate,  in  Carbonic  era,  195. 

in  Champlain  period,  262. 

in  Glacial  period,  256. 

in  Tertiary  era,  242. 

progress  of,  in  geological  time,  283. 

sudden  change  of,  at  close  of  Champlain 

period,  271. 
Clinometer,  7. 
Clinton  group,  165. 
Coal,  impurities  of,  189. 

kinds  of,  189. 

origin  of,  190. 

sulphur  in,  190. 

Coal-areas     in     eastern     North    America, 
188. 

in  Europe,  188. 

in  Eocky  Mountain  region,  228. 
Coal-beds  in  Carboniferous,  189. 

in  Cretaceous,  228. 

in  Triassic,  210. 

thickness  of,  189. 
Coal-measures,  187. 

thickness  of,  188. 
Coccoliths,  50. 
Coccosteus,  182. 
Cockroaches,  169,  195. 
Colorado,  canon  of,  86,  102,  280. 
Columnar  structure,  87. 
Columnaria,  155,  156. 
Conformable  strata,  118. 
Conglomerate,  80. 
Conifers,  Carboniferous,  191,  195. 

Cretaceous,  280. 

Devonian,  175. 

Triassic  and  Jurassic,  214. 
Connecticut  River,  terraces  of,  276. 
Connecticut  Valley,  footprints  in,  219. 

sandstones,  209. 


INDEX. 


295 


trap  ridges,  119. 

trap  rocks,  211. 

Continents,  bordered  by  mountain  ranges, 
116. 

defined  in  Archaean  time,  138. 

origin  of,  120. 
Contraction  of  earth,  a  cause  of  change  of 

level,  116. 

Contraction  of  rocks,  effect  of,  84. 
Cooling  of  globe,  effects  of,  116,  120. 
Copper  ores,  28,  29. 
Coral  reefs  and  islands,  73. 
Corallines,  50. 
Corals,  43.  126. 

Cambrian,  147. 

Carbonic,  187,  195. 

Devonian,  176. 

Lower  Silurian,  155. 

Triassic  and  Jurassic,  214. 

Upper  Silurian,  168. 
Cordaites,  175. 
Corniferous  limestone,  171. 
Coscinodiscus,  52. 
Cotopaxi,  86. 
Crassatella,  242. 
Crepidula,  243. 
Cretaceous  period,  209,  226. 

map  of  North  America  in,  227. 
Crevasses,  81. 

Crickets,  Carboniferous,  195. 
Crinoidal  limestone,  50,  186. 
Crinoids,  46, 127. 

Cambrian,  147. 

Carbonic,  186, 195. 

Devonian,  176. 

Lower  Silurian,  155,  156. 

Triassic  and  Jurassic,  214. 

Tipper  Silurian,  168. 
Crocodiles,  222,  232,  244. 
Cro-Magnon  skull,  274. 
Crustaceans,  131. 

Cambrian,  149,  151. 

Carboniferous,  195. 

Devonian,  176,  178. 

Lower  Silurian,  158. 

Upper  Silurian,  168,  169. 
Cryptogams,  Cambrian,  147. 

Carboniferous,  191. 

Devonian,  178. 

Lower  Silurian,  154. 

Triassic  and  Jurassic,  214. 

Upper  Silurian,  167. 
Crystalline  rocks,  31,  93. 

structure,  14. 

Culmination  of  types,  286. 
Cuneolina,  48,  230. 
Currents,  oceanic,  74. 

wind-made,  72. 


Cyanite,  23. 

Cyathophylloid  corals,  155,  168,  176, 185. 

Cycads,  176,  214,  230. 

Cycas,  213. 

Cypraaa,  248. 

DAPEDIUS,  219. 

Da\vkins,  W.  B.,  on  human  relics,  275. 

Decapods,  150. 

Decay  of  rocks,  58. 

Deep-sea  life,  56. 

Deer,  Irish,  267. 

Delta  of  Mississippi,  66. 

Denudation,  66. 

Devonian  era,  125,  145,  170. 

hornstone,  171. 
Diamond,  14. 
Diatoms,  51. 
Diceras,  215,  216. 
Dictyocha,  52. 
Dikes,  85. 

Dinosaurs,  220,  229,  232. 
Dip,  108. 

Dipnoans,  179,  182. 
Dipterus,  180. 
Dismal  Swamp,  58. 
Dodo,  278. 

Doleryte.    See  TRAP. 
Dolomite,  24,  29. 
Drift,  250. 

sands,  61. 

scratches,  253. 
Dromatherium,  226. 
Dunes,  61. 
Dynamical  geology,  39. 

EARLY  Paleozoic,  145. 

Earth,  earliest  condition  of,  137. 

progress  in  features,  282. 
Earthquakes,  114. 
Eifel  limestone,  172. 

Elephant,  picture  of,  engraved  on  ivory,  273. 
Elephants,  Quaternary,  268,  269,  271. 

Tertiary,  246. 
Embryology    and    paleontology,  parallelism 

of,  287. 
Emery,  19. 
Enaliosaurs,  222,  232. 
England,  geological  map  of,  212. 
Eoblattina,  196. 
Eocene  period,  237. 
Eozoon,  143. 
Ephemera',  178. 
Epidote,  23. 
Equiseta,  Carboniferous,  191,  193. 

Devonian,  173. 

Eras,  geological,  table  of,  135. 
Erosion,  64,  70. 


296 


INDEX. 


Eschara,  128. 

Euplectella,  55. 

Eurylepis,  197. 

Evolution,  285. 

Exogyra,  215,  216. 

Expansion  of  rocks,  effect  of,  84. 

FALSE  Topaz,  17. 

Faults,  112,  205. 

Favosites,  176. 

Features  of  earth,  development  of,  282. 

Feldspar,  20. 

Ferns,  Carboniferous,  191. 

Devonian,  173. 

Triassic  and  Jurassic,  214. 
Fingal's  Cave,  248. 
Fishes,  132,  133. 

Carbonic,  196. 

Cretaceous,  232. 

Devonian,  179. 

Lower  Silurian,  159 

reign  of,  125,  145. 

Tertiary.  243. 

Triassic  and  Jurassic,  218. 

Upper  Silurian,  168,  169. 
Fish-spines,  179. 
Flabellina,  48,  230. 
Flabellum,  46. 
Flags,  31,  172. 
Flexures  of  strata,  109. 
Flint,  17,  54. 

arrow-heads,  271. 
Folded  rocks,  109. 
Footprints.    See  TRACKS. 
Foraminifers,  48. 
Fordilla,  149. 

Fossils,  criterion  of  age  of  strata,  123. 
Fractures  of  rocks,  112. 
Fragmental  rocks,  41. 
Freezing,  expansion  in,  78. 
Fresh  waters,  action  of,  63. 
Fringing  reefs,  74. 
Frondicularia,  48. 
Fruits,  fossil,  195. 
Fusion,  rocks  formed  from,  89. 
Fusulina,  48. 

GALENA,  28. 

limestone,  154. 
Galenlte,  28. 
Ganoids,  Carboniferous,  196. 

Cretaceous,  232. 

Devonian,  179,  180. 

Lower  Silurian,  159. 

Triassic  and  Jurassic,  218. 

Upper  Silurian,  170. 
Garnet,  22. 
Gars.    See  GANOIDS. 


Gas,  natural,  160. 
Gastropods,  129. 

Cambrian,  148,  151. 
Geological  time,  length  of,  280. 
Geology,  definition  of,  11. 
Geysers,  90. 

Giant's  Causeway,  34,  248. 
Glacial  period,  250. 

cause  of  climate,  256. 

limit  of  ice-sheet  in  North  America,  259. 

phenomena  due  to  glaciers,  254. 

second,  of  Europe,  264,  275. 

thickness  of  ice  in  North  America,  255. 
Glaciers,  79. 

movement  of,  80,  256. 

scratches  made  by,  81,  82,  253.  • 
Globigerina,  48. 
Glyptodon,  270. 
Gneiss,  32. 
Goniatites,  177,  217. 
Corner  Glacier,  80. 
Grammatophora,  51,  52. 
Grammostomuiu,  48. 
Granite,  31. 
Graphite,  14,  143. 
Gravel,  31. 
Green  Mountains,   scratches  and  bowlders 

on,  253. 

Greenland,  changes  of  level  in,  278. 
Greensand,  228,  241. 
Ground  pines.    See  LYCOPODS. 
Gryphsea,  214,  216. 
Gulf  Stream,  74. 
Gymnosperms,  Carboniferous,  191,  195. 

Cretaceous,  230. 

Devonian,  175. 

Triassic  and  Jurassic,  214. 
Gypsiferous  formation,  Triassic,  211. 
Gypsum,  25,  166. 

HADROSAURUS,  222. 

Halonia,  194. 

Halysites,  168. 

Hamilton  group,  172. 

Hammer,  geological,  6. 

Hawaii,  volcanoes  of,  88. 

Heat,  effects  of,  84. 

Height  of  volcanic  peaks,  86. 

Helderberg.  See  LOWER  HELDERBBHG,  UP- 
PER HELDERBERG. 

Hematite,  27, 

Hesperornis,  233. 

Highlands  of  New  York  and  New  Jersey. 
138. 

Himalayas,  elevation  of,  248. 

Hippopotamus,  244,  245. 

Historical  geology,  122. 

Holopea,  151. 


INDEX. 


297 


Holoptychius,  180. 
Homalonotus,  169. 
Hood,  Mount,  248. 
Hornblende,  21,  22. 

schist,  33. 

Hornstone,  17,  54, 171. 
Horses,  Quaternary,  267,  269. 

Tertiary,  246,  246. 
Hot  springs,  90. 
Hudson  Kiver  shales,  154. 
Human  skeletons,  fossil,  274. 
Hyaena,  cave,  267. 
Hydrogen,  14. 
Hydromica  schist,  32. 
Hyolithes,  149. 

ICE,  geological  work  of,  78. 

of  glaciers,  81,  256. 

of  rivers  and  lakes,  78. 
Icebergs,  83. 
Ichthyocrinus,  168. 
Ichthyosaurus,  222. 
Igneous  rocks,  39. 

Tertiary,  248. 

Triassic,  211. 
Iguaiiodon,  222. 
Infusorial  earth,  51. 
Insects,  181. 

Carboniferous,  195. 

Devonian,  178. 

Lower  Silurian,  159. 

Upper  Silurian,  168, 169. 
Invertebrates,  133. 
Irish  deer,  267. 

Iron  Mountains  of  Missouri,  140. 
Iron  ores,  25,  140. 
Isopods,  150. 

JOINTS  in  rocks,  113. 
Jorullo,  87. 
Jurassic  period,  209. 

KILAUEA,  88. 
Kitchen  middens,  278. 

LABRADOKITE,  20. 

Lacertilians.    See  LIZARDS. 

Lakes   of  Rocky   Mountain    region   in  the 

Tertiary,  238. 
Lainellibranchs,  129. 

Cambrian,  148. 

Tertiary,  242. 

Triassic  and  Jurassic,  214. 
Laramide  Mountain  system,  235. 
Later  Paleozoic,  145,  163. 
Lateral  pressure  in  earth's  crust,  115. 
Laurentide  Plateau,  center  of  glaciation  for 
North  America,  257. 


Lava,  33. 
Layer,  36. 
Lead  ore,  28. 
Lepidodendron,  175,  194. 
Lepidoganoids,  179,  180. 
Lepidosteus,  181. 
Leptaena,  157, 168. 
Leptomitus,  148. 

Level,    Quaternary    changes   of,    256,    262, 
275. 

Kecent  changes  of,  in  Sweden,  Green- 
land, and  United  States,  277. 
Lias,  213. 
Lichas,  169. 
Life,  agency  of,  in  rock-making,  43. 

Archffian,  142. 

Cambrian,  147. 

Carbonic,  191. 

changes  of,  at  close  of  Paleozoic,  208. 

Cretaceous,  229. 

Early  Paleozoic,  159. 

Lower  Silurian,  154. 

Pleistocene,  265. 

progress  of,  in  geological  time,  284. 

progress  of,  in  Mesozoic,  233. 

Tertiary,  241. 

Triassic  and  Jurassic,  214. 

Upper  Silurian,  167. 
Lignite,  239. 

Lignitic  beds,  Tertiary,  239. 
Lime,  19. 
Limestone,  24,  29. 

formation  of,  40,  43. 
Limonite,  27. 
Lingulella,  151. 
Lingulepis,  151. 
Lion,  cave,  267. 
Liriodendron,  229. 
Lithostrotion,  185. 
Lituola,  48,  280. 
Lizards,  222,  244. 
Llandeilo  flags,  154. 
Loa,  Mauna,  87,  88. 
Loligo,  130. 

Lower  Helderberg  period,  164,  166. 
Lower  Silurian  era,  125,  145,  153. 
Ludlow  group,  167. 
Lycopods.  Carboniferous,  191, 193. 

Devonian,  174. 

Upper  Silurian,  167. 

MADREPOBA,  44. 
Madrepores,  44. 
Magnesia,  19. 

Magnesian  limestone,  24,  29. 
Magnesium,  14. 
Magnetic  iron  ore,  26. 
Magnetite,  26. 


298 


INDEX. 


Magnolia,  248. 
Malachite,  29. 
Mammals,  138,  184. 

Cretaceous,  288. 

era  of,  125,  287. 

Quaternary,  266. 

Tertiary,  244. 

Triassic  and  Jurassic,  218,  225. 
Man,  era  of,  125,  287,  249. 

fossil  skeletons  of,  274. 

head  of  the  system  of  life,  290. 

origin  of,  289. 

relics  of,  271. 

Mansfield,  Mount,  glacial  scratches  on,  253. 
Map  of  England,  212. 
Map  of  North  America,  Archsean,  189. 

Cretaceous,  227. 

Paleozoic,  164. 

post-Paleozoic,  207. 

Quaternary,  251,  260. 

Tertiary,  238. 
Map  of  United  States.  136. 
Marble,  29. 
Marsupials,  Cretaceous,  238. 

Quaternary,  270. 

Triassic  and  Jurassic,  225. 
Mastodon,  Quaternary,  268. 

Tertiary,  245,  246. 
Mauna  Loa,  87,  88. 
May-flies,  Carboniferous,  195. 

Devonian,  178. 
Medina  sandstone,  165. 
Megalosaur,  221.  • 

Megatherium,  269. 
Melosira,  51,  52. 
Mentone  skeleton,  274. 
Mesas,  107. 
Mesozoic  time,  125,  209. 

progress  of  life  in,  233. 
Metamorphic  rocks,  42,  95. 
Metamorphism,  93, 114. 
Methods  of  study  in  geology,  3. 
Miamia,  196. 
Mica,  21. 

schist,  82. 
Millstone  grit,  187. 
Mineral  coal.    See  COAL. 
Mineral  oil.    See  OIL. 
Miocene  period,  237. 
Mississippi  River,  delta  of,  66. 

sediment  of,  66. 

Mississippi  Valley  in  Quaternary,  264. 
Missouri  iron  ores,  140. 
Moa,  278. 
Molluscoids,  127. 

Cambrian,  148,  151. 

Carboniferous,  195. 

Devonian,  176. 


Lower  Silurian,  157. 

Subcarboniferous,  186. 

Upper  Silurian,  168. 
Mollusks,  128. 

Cambrian,  148,  151. 

Carboniferous,  195. 

Cretaceous,  231. 

Devonian,  177. 

Lower  Silurian,  157. 

Tertiary,  242. 

Triassic  and  Jurassic,  214. 
Monocline,  112. 
Monotremes,  225,  226,  288. 
Monument  Park,  107. 
Moraine,  82. 
Mosasaur,  232. 
Mountain  chains,  118. 
Mountain    ranges,  making  of  material   for, 

114. 
Mountain-making,  cause  of,  115. 

Cenozoic,  246. 

Mesozoic,  234. 

Paleozoic,  161,  183. 

post-Mesozoic,  235. 

post-Paleozoic,  202. 
Mountains  made  by  erosion,  106. 

by  flexures  of  crust,  108. 

by  igneous  ejections,  105. 
Mud,  30. 
Mud-cracks,  76. 
Murchisonia,  129. 
Muscovite,  21. 
Myriapods,  131, 195. 

NATUKE,  system  of,  has  beginning  and  end, 

283. 

Nautilus,  131. 
Navicula,  52. 
Neanderthal  skull,  273. 
Neolithic  epoch,  278. 
Neuropteris,  173,  193. 
New  Jersey  coast,  subsidence  of,  278. 
Niagara  period,  164,  165. 
Niagara  River,  gorge  of,  281. 
Niagara  shale  and  limestone,  165. 
Night  heron,  extinct,  279. 
Nodosaria,  48. 
Non-articulates,  127. 
North  America,  map  of,  Archiwin,  139. 

Cretaceous,  227. 

Paleozoic,  104. 

post-Paleozoic,  207. 

Quaternary,  251,  26(1. 

Tertiary,  238. 
North  America,  Recent  changes  of  level  in, 

278. 

Nova  Scotia  coal  measures,  188,  201. 
Nova  Scotia  range,  206. 


INDEX. 


299 


Nullipores,  50. 
Nummulites,  48,  49,  240. 
Nummulltic  limestone,  240. 
Nuts,  fossil,  195. 

OCEAN,  geological  work  of,  69, 104. 

life  in  depths  of,  56. 
Oceanic  basin,  origin  of,  120. 
Odontidium,  52. 
Oil,  mineral,  160. 
Old  red  sandstone,  172. 
Olenellus,  150. 
Olivine,  23. 

Onondaga  period,  164, 166. 
Onychadus,  181. 
Oolyte,  213. 
Opal,  18. 
Orbulina,  48. 
Ores,  25. 

Organic  remains,  rocks  made  of,  41. 
Oriskany  sandstone,  171. 
Orthis,  149,  157,  168. 
Orthisina,  149. 
Orthoceras,  157,  158. 
Orthoclase,  20. 
Ostracoids,  149, 159. 
Ostrea,  216,  242. 
Otozoum,  219. 
Ouachita  range,  207. 
Oxen,  first  of,  246. 
Oxygen,  13. 
Oyster,  Tertiary,  242. 

PAL.SASPIS,  170. 
Palseaster,  156. 
Palseohatteria,  199. 
Palieopalsemon,  178. 
Paleolithic  epoch,  272. 
Paleozoic  time,  125,  144. 

change  in  life  at  close  of,  208. 

geographical  progress  during,  201. 
Palisades,  209,  211. 
Palms,  Cretaceous,  229. 

Tertiary,  242. 
Paradoxides,  151. 
Peat  beds,  57. 
Pelion,  198. 

Pentacrinus,  47,  214,  215. 
Pentremites,  185. 
Permian  period,  191. 
Phsenogams,  Carboniferous,  191,  195. 

Cretaceous,  229. 

Devonian,  175. 

Triassic  and  Jurassic,  214. 
Phillipsastrwa,  176. 
Pinnularia,  51,  52. 
Placenticeras,  231. 
Placoderms,  169, 179, 181. 


Platephemera,  178. 

Platyceras,  149. 

Pleistocene,  250. 

Plesiosaurus,  223. 

Pleurocystites,  156. 

Pleurosigma,  51. 

Pleurotomaria,  129. 

Pliocene  period,  237. 

Plumbago.    See  GRAPHITE. 

Poebrotherium,  246. 

Polycystines.    See  RADIOLARIANS. 

Polyps,  43,  126. 

Polythalamia.    See  FORAMINIFERS. 

Porcellio,  150. 

Porphyry,  85, 

Portage  group,  172. 

Portland  dirt  bed,  218. 

Post-Mesozoic  revolution,  235. 

Post-Paleozoic  revolution,  202. 

Post-Tertiary.    See  QUATERNARY. 

Potash,  19. 

Potassium,  14. 

Potsdam  sandstone,  146,  147. 

Primordial.    See  CAMBRIAN. 

Productus,  186. 

Progress  of  life,  284. 

Protannularia,  155. 

Protocaris,  150. 

Protozoans,  126. 

Archaean,  148. 

Cambrian,  147. 

Cretaceous,  231. 

Lower  Silurian,  155. 

Tertiary,  240. 
Pterichthys,  182. 
Pterodactylus,  224. 
Pteropods,  129, 130,  148. 
Pteropsis,  242. 
Pterosaurs,  223,  229,  232. 
Ptilodictya,  128. 
Pudding-stone,  30. 
Pyrenees,  247. 
Pyrite,  25. 
Pyroxene,  21. 

QUARTZ,  16. 
Quartz-syenyte,  33. 
Quaternary  era,  125,  237,  249. 
Quicklime,  19. 

RADIATES,  126. 

Cambrian,  147. 

Carbonic,  186,  195. 

Devonian,  176. 

Lower  Silurian,  155. 

Triassic  and  Jurassic,  214. 

Upper  Silurian,  168. 
Radiolarians,  53,  126. 


300 


INDEX. 


Rain-prints,  77. 

Raritan  clays,  228. 

Recent  period,  250,  275. 

Reefs,  coral,  73. 

Regional  metamorphism,  94. 

Reindeer  epoch,  265,  272,  275. 

Reptiles,  133. 

Cretaceous,  232. 

Permian,  197. 

reign  of,  125,  209. 

Tertiary,  244. 

Trias&ic  and  Jurassic,  218,  220. 
Reptilian  era,  209. 
Revolution,  post-Mesozoic,  235. 

post-Paleozoic,  202. 
Rhamphorhynchus,  225. 
Rhinoceroses,  Quaternary,  268,  271. 

Tertiary,  244,  245. 
Rhizopods,  48,  126. 

Archsean,  143. 

Cretaceous,  231. 

Lower  Silurian,  155. 
Rhynchonella,  128. 
Ripple-marks,  75. 

River  systems,  development  of,  282. 
River  terraces,  276. 
Rivers,  action  of,  64. 
Roches  moutonnees,  82,  259. 
Rocks,  Archsean,  138. 

calcareous,  29,  43. 

Cambrian,  145. 

Carboniferous,  187. 

Cretaceous,  226. 

crystalline,  81,  93. 

Devonian,  171. 

fragrnental,  29,  41. 

igneous,  39. 

kinds  of,  29. 

Lower  Silurian,  158. 

making  of,  39. 

metamorphic,  42,  95. 

Permian,  191. 

schistose,  82. 

sedimentary,  29,  41. 

solidification  of,  92. 

stratified,  85. 

structure  of,  35. 

Subcarboniferous,  184,  186. 

Tertiary,  287. 

thickness  of  Paleozoic,  161,  203. 

Triassic  and  Jurassic,  209. 

unstratified,  87. 

Upper  Silurian,  165. 
Rocky  Mountain  coal-areas,  228. 
Rocky  Mountains,  elevation  of,  235,  247. 

glaciation  of,  258. 

igneous  rocks  in,  248. 
Rotalia,  48,  49. 


ST.  LAWRENCE  RIVER  in  the  Quaternary,  263. 

St.  Peter's  sandstone,  153. 

Saliferous  group  in  Europe,  211. 

Saliferous  rocks  in  New  York,  166. 

Salina  rocks,  166. 

Salix,  229. 

Salt  of  New  York  and  Canada.  166. 

of  Onondaga  period,  166. 

of  Triassic  period,  211. 
Sand,  30. 

scratches,  63. 
Sand-fleas,  150. 
Sandstone,  29. 
Sapphire,  19. 
Sassafras,  229. 
Scaphites,  231. 
Schist,  schistose  rocks,  32. 
Scoria,  34. 
Scorpions,  Carboniferous,  195. 

Upper  Silurian,  168. 
Scratches,  glacial,  81,  82,  253. 
Sea-beaches,  elevated,  263. 
Sea-saurians,  222,  232. 
Seaweeds,  143,  147, 154,  173. 
Sedimentary  rocks,  great  extent  of,  77. 
Selachians.    See  SHARKS. 
Sequoia,  243. 
Serolis,  150. 
Serpentine,  23. 
Shale,  30. 
Sharks,  Carbonic,  196. 

Cretaceous,  232. 

Devonian,  179. 

Tertiary,  243. 

Upper  Silurian,  170. 
Shasta,  Mount,  86,  248. 
Shells,  rocks  made  of,  43. 
Siderite,  28. 
Sierra  Nevada,  elevation  of,  234. 

glaciation  of,  258. 
Sigillaria,  175,  194. 
Silex,  52. 
Silica,  16. 

action  of,  in  solidification  of  rocks,  92. 
Silicates,  19. 

Siliceous  skeletons  of  animals  and  plants,  51. 
Silicon,  18. 
Silurian.    See  LOWER  SILURIAN,  UPPER  81- 

HTBIAN. 

Skeletons  of  man,  fossil,  274. 

Slate,  31. 

Sloths,  gigantic,  of  Quaternary,  269. 

Snails,  Carboniferous,  195. 

Snakes,  244. 

Soapstone,  22. 

Soda,  20. 

Sodium,  14. 

Solfataras,  90. 


INDEX. 


301 


Solidification  of  rocks,  92. 

Solitaire,  279. 

Solution,  rocks  fanned  from,  40. 

Sow-bugs,  150. 

Spathic  iron  ore,  28. 

Specimens  required  for  study,  5. 

Specular  iron  ore,  27. 

Sphagnum,  57. 

Sphenopteris,  193. 

Spicules  of  sponges,  53,  54. 

Spiders,  131,  195. 

Spirifer,  127,  168,  186. 

Spirocyathus,  148. 

Sponges,  126. 

Cambrian,  147. 

Lower  Silurian,  155. 
Spongiolithis,  52. 
Springs,  hot,  90. 
Squid,  130. 
Stalactite,  40. 
Stalagmite,  40. 

containing  bones  of  cave  animals,  266. 
Star-fishes  155,  156. 
Staurolite,  23. 
Stenotheca,  149. 
Stone  age,  272,  278. 
Strata,  age  of,  how  determined,  123. 

flexures  of,  109. 
Stratified  drift,  254. 
Stratified  rocks,  35. 
Stratum,  defined,  86. 
Streptelasma,  155. 
Strike,  108. 
Styliola,  129. 

Subcarboniferous  period,  184. 
Sulphates,  25. 
Sulphur,  14. 

Sweden,  Recent  changes  of  level  in,  277. 
Syenyte,  33. 
Syenyte-gneiss,  33. 
Syncline,  110. 

TABLE  of  geological  eras,  135. 

Taconic  Mountains,  161. 

Tseniaster,  156. 

Tails  of  fishes,  182. 

Talc,  22. 

Tapir,  244. 

Taxocrinus,  156. 

Teleost  fishes,  232. 

Temperature,  expansion  and  contraction  of 

rocks  by  changes  of,  34. 
Terebratula,  127. 
Terebratulina,  127. 

Terrace  period.     See  RECENT  PERIOD. 
Terraces  along  rivers,  '276. 
Tertiary  era,  125,  237. 
Tetradecapods,  150. 


Textularia,  48. 

Thecocyathus,  45. 

Tides,  geological  i-UVct  of,  69. 

Till,  254. 

Tina',  peologic.il,  length  of,  280. 

Tinoceras,  245. 

Tourmaline,  23. 

Trachyte,  35. 

Tracks  of  reptiles  and  amphibians,  218. 

Trap,  33. 

columnar,  37. 

of  Connecticut  Valley,  211. 
Travertine,  40. 
Tree-ferns,  173,  192. 
Tremolite,  21. 
Trenton  limestone,  153. 
Trenton  period,  153. 
Triarthrus,  158. 
Triassic  period,  209. 
Triceratiutn,  52. 
Triceratops,  233. 
Trigonia,  215,  216. 
Trigonocarpus,  195. 
Trilobites,  Cambrian,  149,  151. 

Carbonic,  195. 

Devonian,  176. 

Lower  Silurian,  158. 

reign  of,  125,  145. 

Upper  Silurian,  168,  169. 
Triloculina,  48. 
Tufa,  85. 

calcareous,  40. 
Turritella,  242. 
Turtles,  222,  282,  244. 

UNOONFORMABLE  strata,  113. 

Underclay,  190. 

United  States,  geological  map  of,  136. 

Unstratified  drift,  254. 

Un  stratified  rocks,  37. 

Upper  Helderberg  limestone,  171. 

Upper  Silurian  era,  125, 145,  164. 

Utica  shales,  154. 

VALLEYS  made  by  erosion,  101. 

by  fractures  of  crust,  104. 

by  upheaval  of  mountains,  104. 
Vapor,  agency  of,  in  volcanoes,  88. 
Veins,  96. 
Vein-stones,  98. 
Venericardia,  242. 
Vertebrates,  181. 

Carbonic,  196. 

Cretaceous,  232. 

Devonian,  179. 

Lower  Silurian,  159. 

Quaternary.  'JCC. 

Tertiary,  243. 


302 


INDEX. 


Triassic  and  Jurassic,  218. 

Upper  Silurian,  168,  169. 
Vesuvius,  88. 

Volcanic  cones,  slopes  of,  87. 
Volcanic  rocks,  33. 
Volcanoes,  85. 

WALDHEIMIA,  127. 

Wasatch  range,  235. 

Washington,  Mount,  bowlders  on,  253. 

Water,  action  of  fresh,  63. 

action  of  oceanic,  69. 

freezing  and  frozen,  78. 
Waterfalls,  65. 
Waves,  action  of,  70. 


Wealden,  212. 

Weathering,  58. 

Wenlock  limestone,  165. 

West  Rock,  210. 

White  Mountains,  alpine  plants  on,  265. 

Wind-drift  structure,  61. 

Winds,  effects  of,  61. 

Woodocrinus,  185. 

Worms,  131,  149,  152,  158. 

XYLOBIUS,  196. 
YELLOWSTONE  PARK,  90. 
ZAPHRENTIS,  168,  176. 


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Phys.Sci.  A    000  642" 783"  5 

QE28         Dana,  James  D. 
2 

Phys.Sci. 

QE28         Dana,  James     D. 

D22 

The  geological  story 
briefly  told. 


>ATE  LOANEDJ 


ISSUED  TO 


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